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  • python networkx

    - by krisdigitx
    hi, i am trying to use networkx with python, when i run this program, it get this error, is there anything missing? #!/usr/bin/env python import networkx as nx import matplotlib import matplotlib.pyplot import matplotlib.pyplot as plt G=nx.Graph() G.add_node(1) G.add_nodes_from([2,3,4,5,6,7,8,9,10]) #nx.draw_graphviz(G) #nx_write_dot(G, 'node.png') nx.draw(G) plt.savefig("/var/www/node.png") Traceback (most recent call last): File "graph.py", line 13, in <module> nx.draw(G) File "/usr/lib/pymodules/python2.5/networkx/drawing/nx_pylab.py", line 124, in draw cf=pylab.gcf() File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf return figure() File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure **kwargs) File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager window = Tk.Tk() File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__ self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use) _tkinter.TclError: no display name and no $DISPLAY environment variable

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  • problem plotting on logscale in matplotlib in python

    - by user248237
    I am trying to plot the following numbers on a log scale as a scatter plot in matplotlib. Both the quantities on the x and y axes have very different scales, and one of the variables has a huge dynamic range (nearly 0 to 12 million roughly) while the other is between nearly 0 and 2. I think it might be good to plot both on a log scale. I tried the following, for a subset of the values of the two variables: fig = plt.figure(figsize(8, 8)) ax = fig.add_subplot(1, 1, 1) ax.set_yscale('log') ax.set_xscale('log') plt.scatter([1.341, 0.1034, 0.6076, 1.4278, 0.0374], [0.37, 0.12, 0.22, 0.4, 0.08]) The x-axes appear log scaled but the points do not appear -- only two points appear. Any idea how to fix this? Also, how can I make this log scale appear on a square axes, so that the correlation between the two variables can be interpreted from the scatter plot? thanks.

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  • How can I plot NaN values as a special color with imshow in matplotlib?

    - by Adam Fraser
    example: import numpy as np import matplotlib.pyplot as plt f = plt.figure() ax = f.add_subplot(111) a = np.arange(25).reshape((5,5)).astype(float) a[3,:] = np.nan ax.imshow(a, interpolation='nearest') f.canvas.draw() The resultant image is unexpectedly all blue (the lowest color in the jet colormap). However, if I do the plotting like this: ax.imshow(a, interpolation='nearest', vmin=0, vmax=24) --then I get something better, but the NaN values are drawn the same color as vmin... Is there a graceful way that I can set NaNs to be drawn with a special color (eg: gray or transparent)?

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  • How can I draw a log-normalized imshow plot with a colorbar representing the raw data in matplotlib

    - by Adam Fraser
    I'm using matplotlib to plot log-normalized images but I would like the original raw image data to be represented in the colorbar rather than the [0-1] interval. I get the feeling there's a more matplotlib'y way of doing this by using some sort of normalization object and not transforming the data beforehand... in any case, there could be negative values in the raw image. import matplotlib.pyplot as plt import numpy as np def log_transform(im): '''returns log(image) scaled to the interval [0,1]''' try: (min, max) = (im[im > 0].min(), im.max()) if (max > min) and (max > 0): return (np.log(im.clip(min, max)) - np.log(min)) / (np.log(max) - np.log(min)) except: pass return im a = np.ones((100,100)) for i in range(100): a[i] = i f = plt.figure() ax = f.add_subplot(111) res = ax.imshow(log_transform(a)) # the colorbar drawn shows [0-1], but I want to see [0-99] cb = f.colorbar(res) I've tried using cb.set_array, but that didn't appear to do anything, and cb.set_clim, but that rescales the colors completely. Thanks in advance for any help :)

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  • numpy array C api

    - by wiso
    I have a C++ function returning a std::vector and I want to use it in python, so I'm using the C numpy api: static PyObject * py_integrate(PyObject *self, PyObject *args){ ... std::vector<double> integral; cpp_function(integral); // this change integral npy_intp size = {integral.size()}; PyObject *out = PyArray_SimpleNewFromData(1, &size, NPY_DOUBLE, &(integral[0])); return out; } when I call it from python, if I do import matplotlib.pyplot as plt a = py_integrate(parameters) print a fig = plt.figure() ax = fig.add_subplot(111) ax.plot(a) print a the first print is ok, the values are correct, but when I plot a they are not, and in particular in the second print I see very strange values like 1E-308 1E-308 ... or 0 0 0 ... as an unitialized memory. I don't understand why the first print is ok.

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  • subplot matplotlib wrong syntax

    - by madptr
    I am using matplotlib to subplot in a loop. For instance, i would like to subplot 49 data sets, and from the doc, i implemented it this way; import numpy as np import matplotlib.pyplot as plt X1=list(range(0,10000,1)) X1 = [ x/float(10) for x in X1 ] nb_mix = 2 parameters = [] for i in range(49): param = [] Y = [0] * len(X1) for j in range(nb_mix): mean = 5* (1 + (np.random.rand() * 2 - 1 ) * 0.5 ) var = 10* (1 + np.random.rand() * 2 - 1 ) scale = 5* ( 1 + (np.random.rand() * 2 - 1) * 0.5 ) Y = [ Y[k] + scale * np.exp(-((X1[k] - mean)/float(var))**2) for k in range(len(X1)) ] param = param + [[mean, var, scale]] ax = plt.subplot(7, 7, i + 1) ax.plot(X1, Y) parameters = parameters + [param] ax.show() However, i have an index out of range error from i=0 onwards. Where can i do better to have it works ? Thanks

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  • making errorbars not clipped in matplotlib with Python

    - by user248237
    I am using matplotlib in Python to plot a line with errorbars as follows: plt.errorbar(xvalues, up_densities, yerr=ctl_sds, fmt='-^', lw=1.2, markersize=markersize, markeredgecolor=up_color, color=up_color, label="My label", clip_on=False) plt.xticks(xvalues) I set the ticks on the x-axis using "xticks". However, the error bars of the last point in xvalues (i.e. xvalues[-1]) are clipped on the right -- meaning only half an error bar appears. This is true even with the clip_on=False option. How can I fix this, so that the error bars appear in full, even though their right side is technically outside xvalues[-1]? thanks.

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  • Send raw data to USB parallel port after upgrading to 11.10

    - by zaphod
    I have a laser cutter connected via a generic USB to parallel adapter. The laser cutter speaks HPGL, as it happens, but since this is a laser cutter and not a plotter, I usually want to generate the HPGL myself, since I care about the ordering, speed, and direction of cuts and so on. In previous versions of Ubuntu, I was able to print to the cutter by copying an HPGL file directly to the corresponding USB "lp" device. For example: cp foo.plt /dev/usblp1 Well, I just upgraded to Ubuntu 11.10 oneiric, and I can't find any "lp" devices in /dev anymore. D'oh! What's the preferred way to send raw data to a parallel port in Ubuntu? I've tried System Settings Printing + Add, hoping that I might be able to associate my device with some kind of "raw printer" driver and print to it with a command like lp -d LaserCutter foo.plt But my USB to parallel adapter doesn't seem to show up in the list. What I do see are my HP Color LaserJet, two USB-to-serial adapters, "Enter URI", and "Network Printer". Meanwhile, over in /dev, I do see /dev/ttyUSB0 and /dev/ttyUSB1 devices for the 2 USB-to-serial adapters. I don't see anything obvious corresponding to the HP printer (which was /dev/usblp0 prior to the upgrade), except for generic USB stuff. For example, sudo find /dev | grep lp produces no output. I do seem to be able to print to the HP printer just fine, though. The printer setup GUI gives it a device URI starting with "hp:" which isn't much help for the parallel adapter. The CUPS administrator's guide makes it sound like I might need to feed it a device URI of the form parallel:/dev/SOMETHING, but of course if I had a /dev/SOMETHING I'd probably just go on writing to it directly. Here's what dmesg says after I disconnect and reconnect the device from the USB port: [ 924.722906] usb 1-1.1.4: USB disconnect, device number 7 [ 959.993002] usb 1-1.1.4: new full speed USB device number 8 using ehci_hcd And here's how it shows up in lsusb -v: Bus 001 Device 008: ID 1a86:7584 QinHeng Electronics CH340S Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 1.10 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 8 idVendor 0x1a86 QinHeng Electronics idProduct 0x7584 CH340S bcdDevice 2.52 iManufacturer 0 iProduct 2 USB2.0-Print iSerial 0 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 32 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0x80 (Bus Powered) MaxPower 96mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 2 bInterfaceClass 7 Printer bInterfaceSubClass 1 Printer bInterfaceProtocol 2 Bidirectional iInterface 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x82 EP 2 IN bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0020 1x 32 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x02 EP 2 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0020 1x 32 bytes bInterval 0 Device Status: 0x0000 (Bus Powered)

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  • Send raw data to USB parallel port after upgrading to 11.10 oneiric

    - by zaphod
    I have a laser cutter connected via a generic USB to parallel adapter. The laser cutter speaks HPGL, as it happens, but since this is a laser cutter and not a plotter, I usually want to generate the HPGL myself, since I care about the ordering, speed, and direction of cuts and so on. In previous versions of Ubuntu, I was able to print to the cutter by copying an HPGL file directly to the corresponding USB "lp" device. For example: cp foo.plt /dev/usblp1 Well, I just upgraded to Ubuntu 11.10 oneiric, and I can't find any "lp" devices in /dev anymore. D'oh! What's the preferred way to send raw data to a parallel port in Ubuntu? I've tried System Settings Printing + Add, hoping that I might be able to associate my device with some kind of "raw printer" driver and print to it with a command like lp -d LaserCutter foo.plt But my USB to parallel adapter doesn't seem to show up in the list. What I do see are my HP Color LaserJet, two USB-to-serial adapters, "Enter URI", and "Network Printer". Meanwhile, over in /dev, I do see /dev/ttyUSB0 and /dev/ttyUSB1 devices for the 2 USB-to-serial adapters. I don't see anything obvious corresponding to the HP printer (which was /dev/usblp0 prior to the upgrade), except for generic USB stuff. For example, sudo find /dev | grep lp produces no output. I do seem to be able to print to the HP printer just fine, though. The printer setup GUI gives it a device URI starting with "hp:" which isn't much help for the parallel adapter. The CUPS administrator's guide makes it sound like I might need to feed it a device URI of the form parallel:/dev/SOMETHING, but of course if I had a /dev/SOMETHING I'd probably just go on writing to it directly. Here's what dmesg says after I disconnect and reconnect the device from the USB port: [ 924.722906] usb 1-1.1.4: USB disconnect, device number 7 [ 959.993002] usb 1-1.1.4: new full speed USB device number 8 using ehci_hcd And here's how it shows up in lsusb -v: Bus 001 Device 008: ID 1a86:7584 QinHeng Electronics CH340S Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 1.10 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 8 idVendor 0x1a86 QinHeng Electronics idProduct 0x7584 CH340S bcdDevice 2.52 iManufacturer 0 iProduct 2 USB2.0-Print iSerial 0 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 32 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0x80 (Bus Powered) MaxPower 96mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 2 bInterfaceClass 7 Printer bInterfaceSubClass 1 Printer bInterfaceProtocol 2 Bidirectional iInterface 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x82 EP 2 IN bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0020 1x 32 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x02 EP 2 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0020 1x 32 bytes bInterval 0 Device Status: 0x0000 (Bus Powered)

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  • I am getting this error on using matplotlib

    - by Arun Abraham
    I get this error on typing this in python command prompt: import matplotlib.pyplot as plt Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> import matplotlib.pyplot as plt File "/Library/Python/2.7/site-packages/matplotlib-1.3.x-py2.7-macosx-10.8-intel.egg/matplotlib/pyplot.py", line 97, in <module> _backend_mod, new_figure_manager, draw_if_interactive, _show = pylab_setup() File "/Library/Python/2.7/site-packages/matplotlib-1.3.x-py2.7-macosx-10.8-intel.egg/matplotlib/backends/__init__.py", line 25, in pylab_setup globals(),locals(),[backend_name]) File "/Library/Python/2.7/site-packages/matplotlib-1.3.x-py2.7-macosx-10.8-intel.egg/matplotlib/backends/backend_macosx.py", line 21, in <module> from matplotlib.backends import _macosx ImportError: dlopen(/Library/Python/2.7/site-packages/matplotlib-1.3.x-py2.7-macosx-10.8-intel.egg/matplotlib/backends/_macosx.so, 2): Library not loaded: /System/Library/Frameworks/CoreText.framework/Versions/A/CoreText Referenced from: /Library/Python/2.7/site-packages/matplotlib-1.3.x-py2.7-macosx-10.8-intel.egg/matplotlib/backends/_macosx.so Reason: image not found Can someone suggest me, how i can fix this ? I had installed all the packages with this shell script https://github.com/fonnesbeck/ScipySuperpack Is there anything that i am missing ? Any additional configuration ?

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  • Web development: Haskell or Scheme

    - by Robert E. Lester
    I would like to to choose one of these languages for building web applications. I'm not interested in framework per say, but have the following needs: Rapid development. Easy to scale. Strong community for the web. Quick and easy to deploy. I'm very familiar with Haskell, and have some familiarity with scheme (in particular PLT). Scheme appeals to me as good candidate for web development due to it's simple syntax which is homogenous across libraries. I state this despite my subjective opinion that Haskell is a 'cleaner' language. Haskell web apps seem to require learning and building a patchwork of different combinator libraries. On the plus side, I realise this can be quite expressive, although I'd prefer to eliminate impedance mismatches where possible. While scheme-plt looks to be a good fit, I can find but one example of it being used in the "real world". Haskell doesn't seem to fair too much better here, but there seems to be a bigger community behind the web side. Please help me make up my mind. For the most part I'm interested in real-world use cases.

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  • how to set a fixed color bar for pcolor in python matplotlib?

    - by user248237
    I am using pcolor with a custom color map to plot a matrix of values. I set my color map so that low values are white and high values are red, as shown below. All of my matrices have values between 0 and 20 (inclusive) and I'd like 20 to always be pure red and 0 to always be pure white, even if the matrix has values that don't span the entire range. For example, if my matrix only has values between 2 and 7, I don't want it to plot 2 as white and 7 as red, but rather color it as if the range is still 0 to 20. How can I do this? I tried using the "ticks=" option of colorbar but it did not work. Here is my current code (assume "my_matrix" contains the values to be plotted): cdict = {'red': ((0.0, 1.0, 1.0), (0.5, 1.0, 1.0), (1.0, 1.0, 1.0)), 'green': ((0.0, 1.0, 1.0), (0.5, 1.0, 1.0), (1.0, 0.0, 0.0)), 'blue': ((0.0, 1.0, 1.0), (0.5, 1.0, 1.0), (1.0, 0.0, 0.0))} my_cmap = matplotlib.colors.LinearSegmentedColormap('my_colormap', cdict, 256) colored_matrix = plt.pcolor(my_matrix, cmap=my_cmap) plt.colorbar(colored_matrix, ticks=[0, 5, 10, 15, 20]) any idea how I can fix this to get the right result? thanks very much.

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  • Matplotlib plotting non uniform data in 3D surface

    - by Raj Tendulkar
    I have a simple code to plot the points in 3D for Matplotlib as below - from mpl_toolkits.mplot3d import axes3d import matplotlib.pyplot as plt import numpy as np from numpy import genfromtxt import csv fig = plt.figure() ax = fig.add_subplot(111, projection='3d') my_data = genfromtxt('points1.csv', delimiter=',') points1X = my_data[:,0] points1Y = my_data[:,1] points1Z = my_data[:,2] ## I remove the header of the CSV File. points1X = np.delete(points1X, 0) points1Y = np.delete(points1Y, 0) points1Z = np.delete(points1Z, 0) # Convert the array to 1D array points1X = np.reshape(points1X,points1X.size) points1Y = np.reshape(points1Y,points1Y.size) points1Z = np.reshape(points1Z,points1Z.size) my_data = genfromtxt('points2.csv', delimiter=',') points2X = my_data[:,0] points2Y = my_data[:,1] points2Z = my_data[:,2] ## I remove the header of the CSV File. points2X = np.delete(points2X, 0) points2Y = np.delete(points2Y, 0) points2Z = np.delete(points2Z, 0) # Convert the array to 1D array points2X = np.reshape(points2X,points2X.size) points2Y = np.reshape(points2Y,points2Y.size) points2Z = np.reshape(points2Z,points2Z.size) ax.plot(points1X, points1Y, points1Z, 'd', markersize=8, markerfacecolor='red', label='points1') ax.plot(points2X, points2Y, points2Z, 'd', markersize=8, markerfacecolor='blue', label='points2') plt.show() My problem is that I tried to make a decent surface plot out of these data points that I have. I already tried to use ax.plot_surface() function to make it look nice. For this I eliminated some points, and recalculated the matrix kind of input needed by this function. However, the graph I generated was far more difficult to interpret and understand. So there might be 2 possibilities: either I am not using the function correctly, or otherwise, the data I am trying to plot is not good for the surface plot. What I was expecting was 3D graph which would have an effect similar to that we have of 3D pie chart. We see that one piece (that which is extracted out) is part of another piece. I was not expecting it to be exactly same like that, but some kind of effect like that. What I would like to ask is: Do you think it will be possible to make such 3D graph? Is there any way better, I could express my data in 3 dimension? Here are the 2 files - points1.csv Dim1,Dim2,Dim3 3,8,1 3,8,2 3,8,3 3,8,4 3,8,5 3,9,1 3,9,2 3,9,3 3,9,4 3,9,5 3,10,1 3,10,2 3,10,3 3,10,4 3,10,5 3,11,1 3,11,2 3,11,3 3,11,4 3,11,5 3,12,1 3,12,2 3,13,1 3,13,2 3,14,1 3,14,2 3,15,1 3,15,2 3,16,1 3,16,2 3,17,1 3,17,2 3,18,1 3,18,2 4,8,1 4,8,2 4,8,3 4,8,4 4,8,5 4,9,1 4,9,2 4,9,3 4,9,4 4,9,5 4,10,1 4,10,2 4,10,3 4,10,4 4,10,5 4,11,1 4,11,2 4,11,3 4,11,4 4,11,5 4,12,1 4,13,1 4,14,1 4,15,1 4,16,1 4,17,1 4,18,1 5,8,1 5,8,2 5,8,3 5,8,4 5,8,5 5,9,1 5,9,2 5,9,3 5,9,4 5,9,5 5,10,1 5,10,2 5,10,3 5,10,4 5,10,5 5,11,1 5,11,2 5,11,3 5,11,4 5,11,5 5,12,1 5,13,1 5,14,1 5,15,1 5,16,1 5,17,1 5,18,1 6,8,1 6,8,2 6,8,3 6,8,4 6,8,5 6,9,1 6,9,2 6,9,3 6,9,4 6,9,5 6,10,1 6,11,1 6,12,1 6,13,1 6,14,1 6,15,1 6,16,1 6,17,1 6,18,1 7,8,1 7,8,2 7,8,3 7,8,4 7,8,5 7,9,1 7,9,2 7,9,3 7,9,4 7,9,5 and points2.csv Dim1,Dim2,Dim3 3,12,3 3,12,4 3,12,5 3,13,3 3,13,4 3,13,5 3,14,3 3,14,4 3,14,5 3,15,3 3,15,4 3,15,5 3,16,3 3,16,4 3,16,5 3,17,3 3,17,4 3,17,5 3,18,3 3,18,4 3,18,5 4,12,2 4,12,3 4,12,4 4,12,5 4,13,2 4,13,3 4,13,4 4,13,5 4,14,2 4,14,3 4,14,4 4,14,5 4,15,2 4,15,3 4,15,4 4,15,5 4,16,2 4,16,3 4,16,4 4,16,5 4,17,2 4,17,3 4,17,4 4,17,5 4,18,2 4,18,3 4,18,4 4,18,5 5,12,2 5,12,3 5,12,4 5,12,5 5,13,2 5,13,3 5,13,4 5,13,5 5,14,2 5,14,3 5,14,4 5,14,5 5,15,2 5,15,3 5,15,4 5,15,5 5,16,2 5,16,3 5,16,4 5,16,5 5,17,2 5,17,3 5,17,4 5,17,5 5,18,2 5,18,3 5,18,4 5,18,5 6,10,2 6,10,3 6,10,4 6,10,5 6,11,2 6,11,3 6,11,4 6,11,5 6,12,2 6,12,3 6,12,4 6,12,5 6,13,2 6,13,3 6,13,4 6,13,5 6,14,2 6,14,3 6,14,4 6,14,5 6,15,2 6,15,3 6,15,4 6,15,5 6,16,2 6,16,3 6,16,4 6,16,5 6,17,2 6,17,3 6,17,4 6,17,5 6,18,2 6,18,3 6,18,4 6,18,5 7,10,1 7,10,2 7,10,3 7,10,4 7,10,5 7,11,1 7,11,2 7,11,3 7,11,4 7,11,5 7,12,1 7,12,2 7,12,3 7,12,4 7,12,5 7,13,1 7,13,2 7,13,3 7,13,4 7,13,5 7,14,1 7,14,2 7,14,3 7,14,4 7,14,5 7,15,1 7,15,2 7,15,3 7,15,4 7,15,5 7,16,1 7,16,2 7,16,3 7,16,4 7,16,5 7,17,1 7,17,2 7,17,3 7,17,4 7,17,5 7,18,1 7,18,2 7,18,3 7,18,4 7,18,5

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  • Why isn't there a good scheme/lisp on llvm?

    - by anon
    There is Gambit scheme, MIT scheme, PLT scheme, chicken scheme, bigloo, larceny, ...; then there are all the lisps. Yet, there's not (to my knowledge) a single popular scheme/lisp on LLVM, even though LLVM provides lots of nice things like: easier to generate code than x85 easy to make C ffi calls ... So why is it that there isn't a good scheme/lisp on LLVM?

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  • Is LuaJIT really faster than every other JIT-ed dynamic languages?

    - by Gabriel Cuvillier
    According to the computer language benchmark game, the LuaJIT implementation seems to beat every other JIT-ed dynamic language (V8, Tracemonkey, PLT Scheme, Erlang HIPE) by an order of magnitude. I know that these benchmarks are not representative (as they say: "Which programming language implementations have the fastest benchmark programs?"), but this is still really impressive. In practice, is it really the case? Someone have tested that Lua implementation?

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  • Estimating the boundary of arbitrarily distributed data

    - by Dave
    I have two dimensional discrete spatial data. I would like to make an approximation of the spatial boundaries of this data so that I can produce a plot with another dataset on top of it. Ideally, this would be an ordered set of (x,y) points that matplotlib can plot with the plt.Polygon() patch. My initial attempt is very inelegant: I place a fine grid over the data, and where data is found in a cell, a square matplotlib patch is created of that cell. The resolution of the boundary thus depends on the sampling frequency of the grid. Here is an example, where the grey region are the cells containing data, black where no data exists. OK, problem solved - why am I still here? Well.... I'd like a more "elegant" solution, or at least one that is faster (ie. I don't want to get on with "real" work, I'd like to have some fun with this!). The best way I can think of is a ray-tracing approach - eg: from xmin to xmax, at y=ymin, check if data boundary crossed in intervals dx y=ymin+dy, do 1 do 1-2, but now sample in y An alternative is defining a centre, and sampling in r-theta space - ie radial spokes in dtheta increments. Both would produce a set of (x,y) points, but then how do I order/link neighbouring points them to create the boundary? A nearest neighbour approach is not appropriate as, for example (to borrow from Geography), an isthmus (think of Panama connecting N&S America) could then close off and isolate regions. This also might not deal very well with the holes seen in the data, which I would like to represent as a different plt.Polygon. The solution perhaps comes from solving an area maximisation problem. For a set of points defining the data limits, what is the maximum contiguous area contained within those points To form the enclosed area, what are the neighbouring points for the nth point? How will the holes be treated in this scheme - is this erring into topology now? Apologies, much of this is me thinking out loud. I'd be grateful for some hints, suggestions or solutions. I suspect this is an oft-studied problem with many solution techniques, but I'm looking for something simple to code and quick to run... I guess everyone is, really! Cheers, David

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  • Are incremental Macro definition possible?

    - by Davorak
    I often find the following type of incremental definition useful: (define (foo) (display "bar")) (foo) ;prints bar (define foo (let ((bar foo)) (lambda () (display "foo") (bar)))) (foo) ;prints foobar How do I preform this type of incremental definition with macros? I could not get let-syntax to provide the same functionality. Currently I use plt scheme, but would like to see answers in different lisp implementations as well.

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  • Is incremental Macro definition possible?

    - by Davorak
    I often find the following type of incremental definition useful: (define (foo) (display "bar")) (foo) ;prints bar (define foo (let ((bar foo)) (lambda () (display "foo") (bar)))) (foo) ;prints foobar How do I preform this type of incremental definition with macros? I could not get let-syntax to provide the same functionality. Currently I use plt scheme, but would like to see answers in different lisp implementations as well.

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  • pymatplotlib without xserver

    - by vigilant
    Is it possible to use networkx or pymatplotlib without an xserver running? I keep getting the following error with their first example (of networkx): Traceback (most recent call last): File "test.py", line 17, in <module> nx.draw(G,pos,node_color='#A0CBE2',edge_color=colors,width=4,edge_cmap=plt.cm.Blues,with_labels=False) File "/usr/local/lib/python2.6/dist-packages/networkx-1.3-py2.6.egg/networkx/drawing/nx_pylab.py", line 124, in draw cf=pylab.gcf() File "/usr/lib/pymodules/python2.6/matplotlib/pyplot.py", line 276, in gcf return figure() File "/usr/lib/pymodules/python2.6/matplotlib/pyplot.py", line 254, in figure **kwargs) File "/usr/lib/pymodules/python2.6/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager window = Tk.Tk() File "/usr/lib/python2.6/lib-tk/Tkinter.py", line 1646, in __init__ self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use) _tkinter.TclError: couldn't connect to display ""

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  • Solaris X86 64-bit Assembly Programming

    - by danx
    Solaris X86 64-bit Assembly Programming This is a simple example on writing, compiling, and debugging Solaris 64-bit x86 assembly language with a C program. This is also referred to as "AMD64" assembly. The term "AMD64" is used in an inclusive sense to refer to all X86 64-bit processors, whether AMD Opteron family or Intel 64 processor family. Both run Solaris x86. I'm keeping this example simple mainly to illustrate how everything comes together—compiler, assembler, linker, and debugger when using assembly language. The example I'm using here is a C program that calls an assembly language program passing a C string. The assembly language program takes the C string and calls printf() with it to print the string. AMD64 Register Usage But first let's review the use of AMD64 registers. AMD64 has several 64-bit registers, some special purpose (such as the stack pointer) and others general purpose. By convention, Solaris follows the AMD64 ABI in register usage, which is the same used by Linux, but different from Microsoft Windows in usage (such as which registers are used to pass parameters). This blog will only discuss conventions for Linux and Solaris. The following chart shows how AMD64 registers are used. The first six parameters to a function are passed through registers. If there's more than six parameters, parameter 7 and above are pushed on the stack before calling the function. The stack is also used to save temporary "stack" variables for use by a function. 64-bit Register Usage %rip Instruction Pointer points to the current instruction %rsp Stack Pointer %rbp Frame Pointer (saved stack pointer pointing to parameters on stack) %rdi Function Parameter 1 %rsi Function Parameter 2 %rdx Function Parameter 3 %rcx Function Parameter 4 %r8 Function Parameter 5 %r9 Function Parameter 6 %rax Function return value %r10, %r11 Temporary registers (need not be saved before used) %rbx, %r12, %r13, %r14, %r15 Temporary registers, but must be saved before use and restored before returning from the current function (usually with the push and pop instructions). 32-, 16-, and 8-bit registers To access the lower 32-, 16-, or 8-bits of a 64-bit register use the following: 64-bit register Least significant 32-bits Least significant 16-bits Least significant 8-bits %rax%eax%ax%al %rbx%ebx%bx%bl %rcx%ecx%cx%cl %rdx%edx%dx%dl %rsi%esi%si%sil %rdi%edi%di%axl %rbp%ebp%bp%bp %rsp%esp%sp%spl %r9%r9d%r9w%r9b %r10%r10d%r10w%r10b %r11%r11d%r11w%r11b %r12%r12d%r12w%r12b %r13%r13d%r13w%r13b %r14%r14d%r14w%r14b %r15%r15d%r15w%r15b %r16%r16d%r16w%r16b There's other registers present, such as the 64-bit %mm registers, 128-bit %xmm registers, 256-bit %ymm registers, and 512-bit %zmm registers. Except for %mm registers, these registers may not present on older AMD64 processors. Assembly Source The following is the source for a C program, helloas1.c, that calls an assembly function, hello_asm(). $ cat helloas1.c extern void hello_asm(char *s); int main(void) { hello_asm("Hello, World!"); } The assembly function called above, hello_asm(), is defined below. $ cat helloas2.s /* * helloas2.s * To build: * cc -m64 -o helloas2-cpp.s -D_ASM -E helloas2.s * cc -m64 -c -o helloas2.o helloas2-cpp.s */ #if defined(lint) || defined(__lint) /* ARGSUSED */ void hello_asm(char *s) { } #else /* lint */ #include <sys/asm_linkage.h> .extern printf ENTRY_NP(hello_asm) // Setup printf parameters on stack mov %rdi, %rsi // P2 (%rsi) is string variable lea .printf_string, %rdi // P1 (%rdi) is printf format string call printf ret SET_SIZE(hello_asm) // Read-only data .text .align 16 .type .printf_string, @object .printf_string: .ascii "The string is: %s.\n\0" #endif /* lint || __lint */ In the assembly source above, the C skeleton code under "#if defined(lint)" is optionally used for lint to check the interfaces with your C program--very useful to catch nasty interface bugs. The "asm_linkage.h" file includes some handy macros useful for assembly, such as ENTRY_NP(), used to define a program entry point, and SET_SIZE(), used to set the function size in the symbol table. The function hello_asm calls C function printf() by passing two parameters, Parameter 1 (P1) is a printf format string, and P2 is a string variable. The function begins by moving %rdi, which contains Parameter 1 (P1) passed hello_asm, to printf()'s P2, %rsi. Then it sets printf's P1, the format string, by loading the address the address of the format string in %rdi, P1. Finally it calls printf. After returning from printf, the hello_asm function returns itself. Larger, more complex assembly functions usually do more setup than the example above. If a function is returning a value, it would set %rax to the return value. Also, it's typical for a function to save the %rbp and %rsp registers of the calling function and to restore these registers before returning. %rsp contains the stack pointer and %rbp contains the frame pointer. Here is the typical function setup and return sequence for a function: ENTRY_NP(sample_assembly_function) push %rbp // save frame pointer on stack mov %rsp, %rbp // save stack pointer in frame pointer xor %rax, %r4ax // set function return value to 0. mov %rbp, %rsp // restore stack pointer pop %rbp // restore frame pointer ret // return to calling function SET_SIZE(sample_assembly_function) Compiling and Running Assembly Use the Solaris cc command to compile both C and assembly source, and to pre-process assembly source. You can also use GNU gcc instead of cc to compile, if you prefer. The "-m64" option tells the compiler to compile in 64-bit address mode (instead of 32-bit). $ cc -m64 -o helloas2-cpp.s -D_ASM -E helloas2.s $ cc -m64 -c -o helloas2.o helloas2-cpp.s $ cc -m64 -c helloas1.c $ cc -m64 -o hello-asm helloas1.o helloas2.o $ file hello-asm helloas1.o helloas2.o hello-asm: ELF 64-bit LSB executable AMD64 Version 1 [SSE FXSR FPU], dynamically linked, not stripped helloas1.o: ELF 64-bit LSB relocatable AMD64 Version 1 helloas2.o: ELF 64-bit LSB relocatable AMD64 Version 1 $ hello-asm The string is: Hello, World!. Debugging Assembly with MDB MDB is the Solaris system debugger. It can also be used to debug user programs, including assembly and C. The following example runs the above program, hello-asm, under control of the debugger. In the example below I load the program, set a breakpoint at the assembly function hello_asm, display the registers and the first parameter, step through the assembly function, and continue execution. $ mdb hello-asm # Start the debugger > hello_asm:b # Set a breakpoint > ::run # Run the program under the debugger mdb: stop at hello_asm mdb: target stopped at: hello_asm: movq %rdi,%rsi > $C # display function stack ffff80ffbffff6e0 hello_asm() ffff80ffbffff6f0 0x400adc() > $r # display registers %rax = 0x0000000000000000 %r8 = 0x0000000000000000 %rbx = 0xffff80ffbf7f8e70 %r9 = 0x0000000000000000 %rcx = 0x0000000000000000 %r10 = 0x0000000000000000 %rdx = 0xffff80ffbffff718 %r11 = 0xffff80ffbf537db8 %rsi = 0xffff80ffbffff708 %r12 = 0x0000000000000000 %rdi = 0x0000000000400cf8 %r13 = 0x0000000000000000 %r14 = 0x0000000000000000 %r15 = 0x0000000000000000 %cs = 0x0053 %fs = 0x0000 %gs = 0x0000 %ds = 0x0000 %es = 0x0000 %ss = 0x004b %rip = 0x0000000000400c70 hello_asm %rbp = 0xffff80ffbffff6e0 %rsp = 0xffff80ffbffff6c8 %rflags = 0x00000282 id=0 vip=0 vif=0 ac=0 vm=0 rf=0 nt=0 iopl=0x0 status=<of,df,IF,tf,SF,zf,af,pf,cf> %gsbase = 0x0000000000000000 %fsbase = 0xffff80ffbf782a40 %trapno = 0x3 %err = 0x0 > ::dis # disassemble the current instructions hello_asm: movq %rdi,%rsi hello_asm+3: leaq 0x400c90,%rdi hello_asm+0xb: call -0x220 <PLT:printf> hello_asm+0x10: ret 0x400c81: nop 0x400c85: nop 0x400c88: nop 0x400c8c: nop 0x400c90: pushq %rsp 0x400c91: pushq $0x74732065 0x400c96: jb +0x69 <0x400d01> > 0x0000000000400cf8/S # %rdi contains Parameter 1 0x400cf8: Hello, World! > [ # Step and execute 1 instruction mdb: target stopped at: hello_asm+3: leaq 0x400c90,%rdi > [ mdb: target stopped at: hello_asm+0xb: call -0x220 <PLT:printf> > [ The string is: Hello, World!. mdb: target stopped at: hello_asm+0x10: ret > [ mdb: target stopped at: main+0x19: movl $0x0,-0x4(%rbp) > :c # continue program execution mdb: target has terminated > $q # quit the MDB debugger $ In the example above, at the start of function hello_asm(), I display the stack contents with "$C", display the registers contents with "$r", then disassemble the current function with "::dis". The first function parameter, which is a C string, is passed by reference with the string address in %rdi (see the register usage chart above). The address is 0x400cf8, so I print the value of the string with the "/S" MDB command: "0x0000000000400cf8/S". I can also print the contents at an address in several other formats. Here's a few popular formats. For more, see the mdb(1) man page for details. address/S C string address/C ASCII character (1 byte) address/E unsigned decimal (8 bytes) address/U unsigned decimal (4 bytes) address/D signed decimal (4 bytes) address/J hexadecimal (8 bytes) address/X hexadecimal (4 bytes) address/B hexadecimal (1 bytes) address/K pointer in hexadecimal (4 or 8 bytes) address/I disassembled instruction Finally, I step through each machine instruction with the "[" command, which steps over functions. If I wanted to enter a function, I would use the "]" command. Then I continue program execution with ":c", which continues until the program terminates. MDB Basic Cheat Sheet Here's a brief cheat sheet of some of the more common MDB commands useful for assembly debugging. There's an entire set of macros and more powerful commands, especially some for debugging the Solaris kernel, but that's beyond the scope of this example. $C Display function stack with pointers $c Display function stack $e Display external function names $v Display non-zero variables and registers $r Display registers ::fpregs Display floating point (or "media" registers). Includes %st, %xmm, and %ymm registers. ::status Display program status ::run Run the program (followed by optional command line parameters) $q Quit the debugger address:b Set a breakpoint address:d Delete a breakpoint $b Display breakpoints :c Continue program execution after a breakpoint [ Step 1 instruction, but step over function calls ] Step 1 instruction address::dis Disassemble instructions at an address ::events Display events Further Information "Assembly Language Techniques for Oracle Solaris on x86 Platforms" by Paul Lowik (2004). Good tutorial on Solaris x86 optimization with assembly. The Solaris Operating System on x86 Platforms An excellent, detailed tutorial on X86 architecture, with Solaris specifics. By an ex-Sun employee, Frank Hofmann (2005). "AMD64 ABI Features", Solaris 64-bit Developer's Guide contains rules on data types and register usage for Intel 64/AMD64-class processors. (available at docs.oracle.com) Solaris X86 Assembly Language Reference Manual (available at docs.oracle.com) SPARC Assembly Language Reference Manual (available at docs.oracle.com) System V Application Binary Interface (2003) defines the AMD64 ABI for UNIX-class operating systems, including Solaris, Linux, and BSD. Google for it—the original website is gone. cc(1), gcc(1), and mdb(1) man pages.

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  • How do I set a matplotlib colorbar extents?

    - by Adam Fraser
    I'd like to display a colorbar representing an image's raw values along side a matplotlib imshow subplot which displays that image, normalized. I've been able to draw the image and a colorbar successfully like this, but the colorbar min and max values represent the normalized (0,1) image instead of the raw (0,99) image. f = plt.figure() # create toy image im = np.ones((100,100)) for x in range(100): im[x] = x # create imshow subplot ax = f.add_subplot(111) result = ax.imshow(im / im.max()) # Create the colorbar axc, kw = matplotlib.colorbar.make_axes(ax) cb = matplotlib.colorbar.Colorbar(axc, result) # Set the colorbar result.colorbar = cb If someone has a better mastery of the colorbar API, I'd love to hear from you. Thanks! Adam

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  • ./a.out termniated . Garbage output due to smashing of stack . How to remove this error ?

    - by mekasperasky
    #include <iostream> #include <fstream> #include <cstring> using namespace std; typedef unsigned long int WORD; /* Should be 32-bit = 4 bytes */ #define w 32 /* word size in bits */ #define r 12 /* number of rounds */ #define b 16 /* number of bytes in key */ #define c 4 /* number words in key */ /* c = max(1,ceil(8*b/w)) */ #define t 26 /* size of table S = 2*(r+1) words */ WORD S [t],L[c]; /* expanded key table */ WORD P = 0xb7e15163, Q = 0x9e3779b9; /* magic constants */ /* Rotation operators. x must be unsigned, to get logical right shift*/ #define ROTL(x,y) (((x)<<(y&(w-1))) | ((x)>>(w-(y&(w-1))))) #define ROTR(x,y) (((x)>>(y&(w-1))) | ((x)<<(w-(y&(w-1))))) void RC5_ENCRYPT(WORD *pt, WORD *ct) /* 2 WORD input pt/output ct */ { WORD i, A=pt[0]+S[0], B=pt[1]+S[1]; for (i=1; i<=r; i++) { A = ROTL(A^B,B)+S[2*i]; B = ROTL(B^A,A)+S[2*i+1]; } ct [0] = A ; ct [1] = B ; } void RC5_DECRYPT(WORD *ct, WORD *pt) /* 2 WORD input ct/output pt */ { WORD i, B=ct[1], A=ct[ 0]; for (i=r; i>0; i--) { B = ROTR(B-S [2*i+1],A)^A; A = ROTR(A-S [2*i],B)^B; } pt [1] = B-S [1] ;pt [0] = A-S [0]; } void RC5_SETUP(unsigned char *K) /* secret input key K 0...b-1] */ { WORD i, j, k, u=w/8, A, B, L [c]; /* Initialize L, then S, then mix key into S */ for (i=b-1,L[c-1]=0; i!=-1; i--) L[i/u] = (L[i/u]<<8)+K[ i]; for (S [0]=P,i=1; i<t; i++) S [i] = S [i-1]+Q; for (A=B=i=j=k=0; k<3*t; k++,i=(i+1)%t,j=(j+1)%c) /* 3*t > 3*c */ { A = S[i] = ROTL(S [i]+(A+B),3); B = L[j] = ROTL(L[j]+(A+B),(A+B)); } } void printword(WORD A) { WORD k; for (k=0 ;k<w; k+=8) printf("%c"); } int main() { WORD i, j, k,ptext, pt1 [2], pt2 [2], ct [2] = {0,0}; ifstream in("key1.txt"); ifstream in1("plt.txt"); ofstream out1("cpt.txt"); if(!in) { cout << "Cannot open file.\n"; return 1; } if(!in1) { cout << "Cannot open file.\n"; return 1; } unsigned char key[b]; in >> key; in1 >> pt1[0]; in1 >> pt1[0]; if (sizeof(WORD)!=4) printf("RC5 error: WORD has %d bytes.\n",sizeof(WORD)); RC5_SETUP(key); RC5_ENCRYPT(pt1,ct); printf("\n plaintext "); printword(pt1 [0]); printword(pt1 [1]); printf(" ---> ciphertext "); printword(ct [0]); printword(ct [1]); printf("\n"); RC5_SETUP(key); RC5_DECRYPT(ct,pt2); out1<<ct[0]; out1<<ct[1]; out1 <<"\n"; printf("\n plaintext "); printword(pt1 [0]); printword(pt1 [1]); return 0; } Let the plt.txt file contain 101 100 let the key be 111

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  • Optional attribute values in MappedField

    - by David Brooks
    I'm new to Scala and Lift, coming from a slightly odd background in PLT Scheme. I've done a quick search on this topic and found lots of questions but no answers. I'm probably looking in the wrong place. I've been working my way through tutorials on using Mapper to create database-backed objects, and I've hit a stumbling block: what types should be used to stored optional attribute values. For example, a simple ToDo object might comprise a title and an optional deadline (e.g. http://rememberthemilk.com). The former would be a MappedString, but the latter could not be a MappedDateTime since the type constraints on the field require, say, defaultValue to return a Date (rather than a Date or null/false/???). Is an underlying NULL handled by the MappedField subclasses? Or are there optional equivalents to things like MappedInt, MappedString, MappedDateTime that allow the value to be NULL in the database? Or am I approaching this in the wrong way?

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  • Confusion between numpy, scipy, matplotlib and pylab

    - by goFrendiAsgard
    Numpy, scipy, matplotlib, and pylab are common terms among they who use python for scientific computation. I just learn a bit about pylab, and I got a lot of confusion. Whenever I want to import numpy, I can always do: import numpy as np I just consider, that once I do from pylab import * The numpy will be imported as well (with np alias). So basically the second one do more things compared to the first one. There are few things I want to ask. Is it right that pylab is just a wrapper for numpy, scipy and matplotlib? As np is the numpy alias, what is the scipy and matplotlib alias? (as far as I know, plt is alias of matplotlib.pyplot, but I don't know the alias for the matplotlib itself) Thanks in advance.

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