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Search found 44 results on 2 pages for 'pylab'.

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• plotting stem with a continuous line

  - by Abruzzo Forte e Gentile

  Hi All I need to plot a stem plot of my signal using python and matplotlib. I saw the example and the code but the line connecting the black big dot and the x-axis is not a continous line. Do you know whether is possible and how to get a straight line instead? Thank you very much AFG #!/usr/bin/env python from pylab import * x = linspace(0.1, 2*pi, 10) markerline, stemlines, baseline = stem(x, cos(x), '-.') setp(markerline, 'markerfacecolor', 'b') setp(baseline, 'color','r', 'linewidth', 2) show()

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• Is there an easily available implementation of erf() for Python?

  - by rog

  I can implement the error function, erf, myself, but I'd prefer not to. Is there a python package with no external dependencies that contains an implementation of this function? I have found http://pylab.sourceforge.net/packages/included_functions.htmlthis but this seems to be part of some much larger package (and it's not even clear which one!). I'm sorry if this is a naive question - I'm totally new to Python.

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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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• 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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• Python: x-y-plot with matplotlib

  - by kame

  I want to plot some data. The first column contains the x-data. But matplotlib doesnt plot this. Where is my mistake? #fresnel formula import numpy as np from numpy import cos from scipy import * from pylab import plot, show, ylim, yticks from matplotlib import * from pprint import pprint n1 = 1.0 n2 = 1.5 #alpha, beta, intensity data = [ [10, 22, 4.3], [20, 42, 4.2], [30, 62, 3.6], [40, 83, 1.3], [45, 102, 2.8], [50, 123, 3.0], [60, 143, 3.2], [70, 163, 3.8], ] for i in range(len(data)): rhotang1 = (n1 * cos(data[i][0]) - n2 * cos(data[i][1])) rhotang2 = (n1 * cos(data[i][0]) + n2 * cos(data[i][1])) rhotang = rhotang1 / rhotang2 data[i].append(rhotang) #append 4th value pprint(data) x = data[:][0] y1 = data[:][2] y3 = data[:][3] plot(x, y1, x, y3) show() EDIT: http://paste.pocoo.org/show/205534/ But it doesnt work.

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• Confusion Matrix with number of classified/misclassified instances on it (Python/Matplotlib)

  - by Pinkie

  I am plotting a confusion matrix with matplotlib with the following code: from numpy import * import matplotlib.pyplot as plt from pylab import * conf_arr = [[33,2,0,0,0,0,0,0,0,1,3], [3,31,0,0,0,0,0,0,0,0,0], [0,4,41,0,0,0,0,0,0,0,1], [0,1,0,30,0,6,0,0,0,0,1], [0,0,0,0,38,10,0,0,0,0,0], [0,0,0,3,1,39,0,0,0,0,4], [0,2,2,0,4,1,31,0,0,0,2], [0,1,0,0,0,0,0,36,0,2,0], [0,0,0,0,0,0,1,5,37,5,1], [3,0,0,0,0,0,0,0,0,39,0], [0,0,0,0,0,0,0,0,0,0,38] ] norm_conf = [] for i in conf_arr: a = 0 tmp_arr = [] a = sum(i,0) for j in i: tmp_arr.append(float(j)/float(a)) norm_conf.append(tmp_arr) plt.clf() fig = plt.figure() ax = fig.add_subplot(111) res = ax.imshow(array(norm_conf), cmap=cm.jet, interpolation='nearest') cb = fig.colorbar(res) savefig("confmat.png", format="png") But I want to the confusion matrix to show the numbers on it like this graphic (the right one): http://i48.tinypic.com/2e30kup.jpg How can I plot the conf_arr on the graphic?

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• Create a color generator in matplotlib

  - by Brendan

  I have a series of lines that each need to be plotted with a separate colour. Each line is actually made up of several data sets (positive, negative regions etc.) and so I'd like to be able to create a generator that will feed one colour at a time across a spectrum, for example the gist_rainbow map shown here. I have found the following works but it seems very complicated and more importantly difficult to remember, from pylab import * NUM_COLORS = 22 mp = cm.datad['gist_rainbow'] get_color = matplotlib.colors.LinearSegmentedColormap.from_list(mp, colors=['r', 'b'], N=NUM_COLORS) ... # Then in a for loop this_color = get_color(float(i)/NUM_COLORS) Moreover, it does not cover the range of colours in the gist_rainbow map, I have to redefine a map. Maybe a generator is not the best way to do this, if so what is the accepted way?

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• matplotlib: working with range in x-axis

  - by user324333

  Hey Guys, I'm trying to do a basic line graph here, but I can't seem to figure out how to adjust my x axis. And here is the error I get when I try adjusting my range. from pylab import * plot ( range(0,11),[9,4,5,2,3,5,7,12,2,3],'.-',label='sample1' ) plot ( range(0,11),[12,5,33,2,4,5,3,3,22,10],'o-',label='sample2' ) xlabel('x axis') ylabel('y axis') title('my sample graphs') legend(('sample1','sample2')) savefig("sampleg.png",dpi=(640/8)) show() File "C:\Python26\lib\site-packages\matplotlib\axes.py", line 228, in _xy_from_xy raise ValueError("x and y must have same first dimension") ValueError: x and y must have same first dimension I want my range to be a list of strings: ["12/1/2007","12/1/2008", "12/1/2009","12/1/2010"] Any suggestions?

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• Plotting 3D Polygons in python-matplotlib

  - by Developer

  I was unsuccessful browsing web for a solution for the following simple question: How to draw 3D polygon (say a filled rectangle or triangle) using vertices values? I have tried many ideas but all failed, see: from mpl_toolkits.mplot3d import Axes3D from matplotlib.collections import PolyCollection import matplotlib.pyplot as plt fig = plt.figure() ax = Axes3D(fig) x = [0,1,1,0] y = [0,0,1,1] z = [0,1,0,1] verts = [zip(x, y,z)] ax.add_collection3d(PolyCollection(verts),zs=z) plt.show() I appreciate in advance any idea/comment. Updates based on the accepted answer: import mpl_toolkits.mplot3d as a3 import matplotlib.colors as colors import pylab as pl import scipy as sp ax = a3.Axes3D(pl.figure()) for i in range(10000): vtx = sp.rand(3,3) tri = a3.art3d.Poly3DCollection([vtx]) tri.set_color(colors.rgb2hex(sp.rand(3))) tri.set_edgecolor('k') ax.add_collection3d(tri) pl.show() Here is the result:

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• Get information about a function in python, looking at source code

  - by Werner

  Hi, the following code comes from the matplotlib gallery: #!/usr/bin/env python from pylab import * x = array([10, 8, 13, 9, 11, 14, 6, 4, 12, 7, 5]) y = array([8.04, 6.95, 7.58, 8.81, 8.33, 9.96, 7.24, 4.26, 10.84, 4.82, 5.68]) I am new to python, and would like to change the content of x and y from an input file. I have two short questions: I could guess what array means, but once I see it on the code, how can I know to which library it belongs and more information about it? Should I use some kind of python debug commands? How do I insert the content of my input file into x? Thanks

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• show() doesn't redraw anymore

  - by Abruzzo Forte e Gentile

  Hi All I am working in linux and I don't know why using python and matplotlib commands draws me only once the chart I want. The first time I call show() the plot is drawn, wihtout any problem, but not the second time and the following. I close the window showing the chart between the two calls. Do you know why and hot to fix it? Thanks AFG from numpy import * from pylab import * data = array( [ 1,2,3,4,5] ) plot(data) [<matplotlib.lines.Line2D object at 0x90c98ac>] show() # this call shows me a plot #..now I close the window... data = array( [ 1,2,3,4,5,6] ) plot(data) [<matplotlib.lines.Line2D object at 0x92dafec>] show() # this one doesn't shows me anything

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• python how to put data on y-axis when plotting histogram

  - by user3041107

  I don't quite understand how to control y - axis when using plt.hist plot in python. I read my .txt data file - it contains 10 columns with various data. If I want to plot distribution of strain on x axis I take column n.5. But what kind of value appears on y axis ??? Don't understand that. here is the code: import numpy import matplotlib.pyplot as plt from pylab import * from scipy.stats import norm import sys strain = [] infile = sys.argv[1] for line in infile: ret = numpy.loadtxt(infile) strain += list(ret[:,5]) fig = plt.figure() plt.hist(strain, bins = 20) plt.show() Thanks for help!

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• matplotlib plot window won't appear

  - by user1518837

  I'm using Python 2.7.3 in 64-bit. I installed pandas as well as matplotlib 1.1.1, both for 64-bit. Right now, none of my plots are showing. After attempting to plot from several different dataframes, I gave up in frustration and tried the following first example from http://pandas.pydata.org/pandas-docs/dev/visualization.html: INPUT: import matplotlib.pyplot as plt ts = Series(randn(1000), index=date_range ('1/1/2000', periods=1000)) ts = ts.cumsum() ts.plot() pylab.show() OUTPUT: Axes(0.125,0.1;0.775x0.8) And no plot window appeared. Other StackOverflow threads I've read suggested I might be missing DLLs. Any suggestions?

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• How to write PIL image filter for plain pgm format?

  - by Juha

  How can I write a filter for python imaging library for pgm plain ascii format (P2). Problem here is that basic PIL filter assumes constant number of bytes per pixel. My goal is to open feep.pgm with Image.open(). See http://netpbm.sourceforge.net/doc/pgm.html or below. Alternative solution is that I find other well documented ascii grayscale format that is supported by PIL and all major graphics programs. Any suggestions? br, Juha feep.pgm: P2 # feep.pgm 24 7 15 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 3 3 3 0 0 7 7 7 7 0 0 11 11 11 11 0 0 15 15 15 15 0 0 3 0 0 0 0 0 7 0 0 0 0 0 11 0 0 0 0 0 15 0 0 15 0 0 3 3 3 0 0 0 7 7 7 0 0 0 11 11 11 0 0 0 15 15 15 15 0 0 3 0 0 0 0 0 7 0 0 0 0 0 11 0 0 0 0 0 15 0 0 0 0 0 3 0 0 0 0 0 7 7 7 7 0 0 11 11 11 11 0 0 15 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 edit: Thanks for the answer, I works... but I need a solution that uses Image.open(). Most of python programs out there use PIL for graphics manipulation (google: python image open). Thus, I need to be able to register a filter to PIL. Then, I can use any software that uses PIL. I now think mostly scipy, pylab, etc. dependent programs.

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• How to manage multiple python versions ?

  - by Gyom

  short version: how can I get rid of the multiple-versions-of-python nightmare ? long version: over the years, I've used several versions of python, and what is worse, several extensions to python (e.g. pygame, pylab, wxPython...). Each time it was on a different setup, with different OSes, sometimes different architectures (like my old PowerPC mac). Nowadays I'm using a mac (OSX 10.6 on x86-64) and it's a dependency nightmare each time I want to revive script older than a few months. Python itself already comes in three different flavours in /usr/bin (2.5, 2.6, 3.1), but I had to install 2.4 from macports for pygame, something else (cannot remember what) forced me to install all three others from macports as well, so at the end of the day I'm the happy owner of seven (!) instances of python on my system. But that's not the problem, the problem is, none of them has the right (i.e. same set of) libraries installed, some of them are 32bits, some 64bits, and now I'm pretty much lost. For example right now I'm trying to run a three-year-old script (not written by me) which used to use matplotlib/numpy to draw a real-time plot within a rectangle of a wxwidgets window. But I'm failing miserably: py26-wxpython from macports won't install, stock python has wxwidgets included but also has some conflict between 32 bits and 64 bits, and it doesn't have numpy... what a mess ! Obviously, I'm doing things the wrong way. How do you usally cope with all that chaos ?e

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• PySide Qt script doesn't launch from Spyder but works from shell

  - by Maxim Zaslavsky

  I have a weird bug in my project that uses PySide for its Qt GUI, and in response I'm trying to test with simpler code that sets up the environment. Here is the code I am testing with: http://stackoverflow.com/a/6906552/130164 When I launch that from my shell (python test.py), it works perfectly. However, when I run that script in Spyder, I get the following error: Traceback (most recent call last): File "/home/test/Desktop/test/test.py", line 31, in <module> app = QtGui.QApplication(sys.argv) RuntimeError: A QApplication instance already exists. If it helps, I also get the following warning: /usr/lib/pymodules/python2.6/matplotlib/__init__.py:835: UserWarning: This call to matplotlib.use() has no effect because the the backend has already been chosen; matplotlib.use() must be called *before* pylab, matplotlib.pyplot, or matplotlib.backends is imported for the first time. Why does that code work when launched from my shell but not from Spyder? Update: Mata answered that the problem happens because Spyder uses Qt, which makes sense. For now, I've set up execution in Spyder using the "Execute in an external system terminal" option, which doesn't cause errors but doesn't allow debugging, either. Does Spyder have any built-in workarounds to this?

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• Have no idea with python-excel read data file

  - by Protoss Reed

  I am a student and haven't a big expirence to do this work. So problem is next. I have a part of code: import matplotlib.pyplot as plt from pylab import * import cmath def sf(prompt): """ """ error_message = "Value must be integer and greater or equal than zero" while True: val = raw_input(prompt) try: val = float(val) except ValueError: print(error_message) continue if val <= 0: print(error_message) continue return val def petrogen_elements(): """Input and calculations the main parameters for pertogen elements""" print "Please enter Petrogen elements: \r" SiO2 = sf("SiO2: ") Al2O3= sf("Al2O3: ") Na2O = sf("Na2O: ") K2O = sf("K2O: ") petro = [SiO2,TiO2,Al2O3,] Sum = sum(petro) Alcal = Na2O + K2O TypeA lcal= Na2O / K2O Ka= (Na2O + K2O)/ Al2O3 print '-'*20, "\r Alcal: %s \r TypeAlcal: %s \ \r Ka: %s \r" % (Alcal, TypeAlcal,Ka,) petrogen_elements() So the problem is next. I have to load and read excel file and read all data in it. After that program have to calculate for example Alcaline, Type of Alcaline etc. Excel file has only this structure 1 2 3 4 5   1 name1 SiO2 Al2O3 Na2O K2O 2 32 12 0.21 0.1 3 name2 SiO2 Al2O3 Na2O K2O 4 45 8 7.54 5 5 name3 SiO2 Al2O3 Na2O K2O 6. … …. …. … … … All excel file has only 5 columns and unlimited rows. User has choice input data or import excel file. First part of work I have done but it stays a big part Finally I need to read all file and calculate the values. I would be so grateful for some advice

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• How to maintain long-lived python projects w.r.t. dependencies and python versions ?

  - by Gyom

  short version: how can I get rid of the multiple-versions-of-python nightmare ? long version: over the years, I've used several versions of python, and what is worse, several extensions to python (e.g. pygame, pylab, wxPython...). Each time it was on a different setup, with different OSes, sometimes different architectures (like my old PowerPC mac). Nowadays I'm using a mac (OSX 10.6 on x86-64) and it's a dependency nightmare each time I want to revive script older than a few months. Python itself already comes in three different flavours in /usr/bin (2.5, 2.6, 3.1), but I had to install 2.4 from macports for pygame, something else (cannot remember what) forced me to install all three others from macports as well, so at the end of the day I'm the happy owner of seven (!) instances of python on my system. But that's not the problem, the problem is, none of them has the right (i.e. same set of) libraries installed, some of them are 32bits, some 64bits, and now I'm pretty much lost. For example right now I'm trying to run a three-year-old script (not written by me) which used to use matplotlib/numpy to draw a real-time plot within a rectangle of a wxwidgets window. But I'm failing miserably: py26-wxpython from macports won't install, stock python has wxwidgets included but also has some conflict between 32 bits and 64 bits, and it doesn't have numpy... what a mess ! Obviously, I'm doing things the wrong way. How do you usally cope with all that chaos ?

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• Length-1 arrays can be converted to python scalars error? python

  - by Randy

  from numpy import * from pylab import * from math import * def LogisticMap(a,x): return 4.*a*x*(1.-x) def CosineMap(a,x): return a*cos(x/(2.*pi)) def TentMap(a,x): if x>= 0 or x<0.5: return 2.*a*x if x>=0.5 or x<=1.: return 2.*a*(1.-x) a = 0.98 N = 40 xaxis = arange(0.0,N,1.0) Func = CosineMap subplot(211) title(str(Func.func_name) + ' at a=%g and its second iterate' %a) ylabel('X(n+1)') # set y-axis label plot(xaxis,Func(a,xaxis), 'g', antialiased=True) subplot(212) ylabel('X(n+1)') # set y-axis label xlabel('X(n)') # set x-axis label plot(xaxis,Func(a,Func(a,xaxis)), 'bo', antialiased=True) My program is supposed to take any of the three defined functions and plot it. They all take in a value x from the array xaxis from 0 to N and then return the value. I want it to plot a graph of xaxis vs f(xaxis) with f being any of the three above functions. The logisticmap function works fine, but for CosineMap i get the error "only length-1 arrays can be converted to python scalars" and for TentMap i get error "The truth value of an array with more than one element is ambiguous, use a.any() or a.all()". My tent map function is suppose to return 2*a*x if 0<=x<0.5 and it's suppose to return 2*a*(1-x) if 0.5<=0<=1.

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