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• problem with hierarchical clustering in Python

  - by user248237

  I am doing a hierarchical clustering a 2 dimensional matrix by correlation distance metric (i.e. 1 - Pearson correlation). My code is the following (the data is in a variable called "data"): from hcluster import * Y = pdist(data, 'correlation') cluster_type = 'average' Z = linkage(Y, cluster_type) dendrogram(Z) The error I get is: ValueError: Linkage 'Z' contains negative distances. What causes this error? The matrix "data" that I use is simply: [[ 156.651968 2345.168618] [ 158.089968 2032.840106] [ 207.996413 2786.779081] [ 151.885804 2286.70533 ] [ 154.33665 1967.74431 ] [ 150.060182 1931.991169] [ 133.800787 1978.539644] [ 112.743217 1478.903191] [ 125.388905 1422.3247 ]] I don't see how pdist could ever produce negative numbers when taking 1 - pearson correlation. Any ideas on this? thank you.

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• Why does DataInputStream not support integers?

  - by Jason

  I need to read in a list of numbers from a file, none of which are larger than 32767. Originally I was going to use the Scanner class to pull in the data, then I read about DataInputStream. This would work well for me, except that according to the API, it supports all primitive variables EXCEPT ints! Listed are longs, shorts, bytes, chars, booleans, ect, but no ints. I have no need for double precision from the incoming data. Is this a deliberate or unintentional oversight?

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• How can I retrieve the value of a PASTE (copy-pasta) event in a GWT TextBox?

  - by dominicbri7

  Hello fellow SO members, I want to prevent the user from copy-pasting values in my TextBox IF AND ONLY IF the values do not respect a certain condition. For instance, I created a DigitsOnlyTextBox which will be used for phone numbers. I already made it so only Character.isDigit characters can be typed into the box, and the user cannot copy-paste values into it, using : this.sinkEvents(Event.ONPASTE); and public void onBrowserEvent(Event event) { super.onBrowserEvent(event); // Permet d'empêcher le copier-coller, donc d'entrer des caractères non-numériques if (event.getTypeInt() == Event.ONPASTE) { event.stopPropagation(); event.preventDefault(); } } But I'd like to verify if the copy-pasted String is "digits only" and if so, let the event happen (therefore the text added). tl;dr : see title Thank you for your time. Sincerely.

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• PHP float bug: PHP Hangs On Numeric Value

  - by jeroen

  I just read an interesting article about php hanging on certain float numbers, see The Register and Exploring Binary. I never explicitly use floats, I use number_format() to clean my input and display for example prices. Also, as far as I am aware, all input from for example forms are strings until I tell them otherwise so I am supposing that this problem does not affect me. Am I right, or do I need to check for example Wordpress and Squirrelmail installations on my server to see if they cast anything to float? Or better, grep all php files on my servers for float?

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• Speed up math code in C# by writing a C dll?

  - by Projectile Fish

  I have a very large nested for loop in which some multiplications and additions are performed on floating point numbers. for (int i = 0; i < length1; i++) { s = GetS(i); c = GetC(i); for(int j = 0; j < length2; j++) { double oldU = u[j]; u[j] = c * oldU + s * omega[i][j]; omega[i][j] = c * omega[i][j] - s * oldU; } } This loop is taking up the majority of my processing time and is a bottleneck. Would I be likely to see any speed improvements if I rewrite this loop in C and interface to it from C#?

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• Return parent of node in Binary Tree

  - by user188995

  I'm writing a code to return the parent of any node, but I'm getting stuck. I don't want to use any predefined ADTs. //Assume that nodes are represented by numbers from 1...n where 1=root and even //nos.=left child and odd nos=right child. public int parent(Node node){ if (node % 2 == 0){ if (root.left==node) return root; else return parent(root.left); } //same case for right } But this program is not working and giving wrong results. My basic algorithm is that the program starts from the root checks if it is on left or on the right. If it's the child or if the node that was queried else, recurses it with the child.

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• Script Speed vs Memory Usage

  - by Doug Neiner

  I am working on an image generation script in PHP and have gotten it working two ways. One way is slow but uses a limited amount of memory, the second is much faster, but uses 6x the memory . There is no leakage in either script (as far as I can tell). In a limited benchmark, here is how they performed: -------------------------------------------- METHOD | TOTAL TIME | PEAK MEMORY | IMAGES -------------------------------------------- One | 65.626 | 540,036 | 200 Two | 20.207 | 3,269,600 | 200 -------------------------------------------- And here is the average of the previous numbers (if you don't want to do your own math): -------------------------------------------- METHOD | TOTAL TIME | PEAK MEMORY | IMAGES -------------------------------------------- One | 0.328 | 540,036 | 1 Two | 0.101 | 3,269,600 | 1 -------------------------------------------- Which method should I use and why? I anticipate this being used by a high volume of users, with each user making 10-20 requests to this script during a normal visit. I am leaning toward the faster method because though it uses more memory, it is for a 1/3 of the time and would reduce the number of concurrent requests.

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• Python 3.1 - Memory Error during sampling of a large list

  - by jimy

  The input list can be more than 1 million numbers. When I run the following code with smaller 'repeats', its fine; def sample(x): length = 1000000 new_array = random.sample((list(x)),length) return (new_array) def repeat_sample(x): i = 0 repeats = 100 list_of_samples = [] for i in range(repeats): list_of_samples.append(sample(x)) return(list_of_samples) repeat_sample(large_array) However, using high repeats such as the 100 above, results in MemoryError. Traceback is as follows; Traceback (most recent call last): File "C:\Python31\rnd.py", line 221, in <module> STORED_REPEAT_SAMPLE = repeat_sample(STORED_ARRAY) File "C:\Python31\rnd.py", line 129, in repeat_sample list_of_samples.append(sample(x)) File "C:\Python31\rnd.py", line 121, in sample new_array = random.sample((list(x)),length) File "C:\Python31\lib\random.py", line 309, in sample result = [None] * k MemoryError I am assuming I'm running out of memory. I do not know how to get around this problem. Thank you for your time!

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• When using a HiLo ID generation strategy, what types should be used to hold Ids?

  - by UpTheCreek

  I'm asking this from a c#/NHibnernate perspective, but it's generally applicable. The concern is that the HiLo strategy goes though id's pretty quickly, and for example a low record-count table (Such as Users) is sharing from the same set of id's as a high record-count table (Such as comments). So you can potentially get to high numbers quicker that with other strategies. So what do people recommend? Code side: int/uint/long/ulong? DBSide: int/bigint? My feeling is to go with longs and bigingts, but would like a sanity check :)

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• Measuring debug vs release of ASP.NET applications

  - by Alex Angas

  A question at work came up about building ASP.NET applications in release vs debug mode. When researching further (particularly on SO), general advice is that setting <compilation debug="true"> in web.config has a much bigger impact. Has anyone done any testing to get some actual numbers about this? Here's the sort of information I'm looking for (which may give away my experience with testing such things): Execution time | Debug build | Release build -------------------+---------------+--------------- Debug web.config | average 1 | average 2 Retail web.config | average 3 | average 4 Max memory usage | Debug build | Release build -------------------+---------------+--------------- Debug web.config | average 1 | average 2 Retail web.config | average 3 | average 4 Output file size | Debug build | Release build -------------------+---------------+--------------- | size 1 | size 2

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• How to distinguish properties from constants if they both use PascalCasing for naming?

  - by Gishu

  As stated in the framework design guidelines and the WWW in general, the current guideline is to name your constants like this LastTemplateIndex as opposed to LAST_TEMPLATE_INDEX With the PascalCasing approach, how do you differentiate between a Property and a Constant. ErrorCodes.ServerDown is fine. But what about private constants within your class ? I use quite a lot of them for naming magic numbers.. or for expected values in my unit tests and so on. The ALL_CAPS style helps me know that it is a constant . _testApp.SelectTemplate(LAST_TEMPLATE_INDEX); *Disclosure: I have been using the SCREAMING_CAPS style for a while for constants + I find it more readable than squishedTogetherPascalCasedName. It actually STANDS_OUT in a block of text*

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• Splitting a double vector into equal parts

  - by Cosmin

  Greetings, Any input on a way to divide a std::vector into two equal parts ? I need to find the smallest possible difference between |part1 - part2|. This is how I'm doing it now, but from what you can probably tell it will yield a non-optimal split in some cases. auto mid = std::find_if(prim, ultim, [&](double temp) -> bool { if(tempsum >= sum) return true; tempsum += temp; sum -= temp; return false; }); The vector is sorted, highest to lowest, values can indeed appear twice. I'm not expecting part1 and part2 to have the same numbers of elements, but sum(part1) should be as close as possible to sum(part2) For example if we would have { 2.4, 0.12, 1.26, 0.51, 0.70 }, the best split would be { 2.4, 0.12 } and { 1.26, 0.51, 0.70 }. If it helps, I'm trying to achieve the splitting algorithm for the Shannon Fano encoding. Any input is appreciated, thanks!

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• filtering elements from list of lists in Python?

  - by user248237

  I want to filter elements from a list of lists, and iterate over the elements of each element using a lambda. For example, given the list: a = [[1,2,3],[4,5,6]] suppose that I want to keep only elements where the sum of the list is greater than N. I tried writing: filter(lambda x, y, z: x + y + z >= N, a) but I get the error: <lambda>() takes exactly 3 arguments (1 given) How can I iterate while assigning values of each element to x, y, and z? Something like zip, but for arbitrarily long lists. thanks, p.s. I know I can write this using: filter(lambda x: sum(x)..., a) but that's not the point, imagine that these were not numbers but arbitrary elements and I wanted to assign their values to variable names.

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• Parallel Assignment operator in Ruby

  - by Bragaadeesh

  Hi, I was going through an example from Programming in Ruby book. This is that example def fib_up_to(max) i1, i2 = 1, 1 # parallel assignment (i1 = 1 and i2 = 1) while i1 <= max yield i1 i1, i2 = i2, i1+i2 end end fib_up_to(100) {|f| print f, " " } The above program simply prints the fibonacci numbers upto 100. Thats fine. My question here is when i replace the parallel assignment with something like this, i1 = i2 i2 = i1+i2 I am not getting the desired output. My question here is, is it advisable to use parallel assignments? (I come from Java background and it feels really wierd to see this type of assignment) One more doubt is : Is parallel assignment an operator?? Thanks

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• Filtering data in an array.

  - by user276424

  Hi all, I have an array that has 30 date objects. The date objects are indexed in the array from the minimum date value to the maximum date value. What I would like to do is retrieve only 7 dates from the array. Out of the 7, the first one should be the minDate and the last should be the maxDate, with 5 dates in the middle. The 7 numbers should increment evenly from the minDate to the maxDate. How would I accomplish this? Hope I was clear. Thanks, Tonih

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• best way to output a full precision double into a text file

  - by flevine100

  Hi, I need to use an existing text file to store some very precise values. When read back in, the numbers essentially need to be exactly equivalent to the ones that were originally written. Now, a normal person would use a binary file... for a number of reasons, that's not possible in this case. So... do any of you have a good way of encoding a double as a string of characters (aside from increasing the precision). My first thought was to cast the double to a char[] and write out the chars. I don't think that's going to work because some of the characters are not visible, produce sounds, and even terminate strings ('\0'... I'm talkin to you!) Thoughts?

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• How can I create numbered map markers in Google Maps V3?

  - by kaneuniversal

  I'm working on a map that has multiple markers on it. These markers use a custom icon, but I'd also like to add numbers on top. I've seen how this has been accomplished using older versions of the API. How can I do this in V3? *Note -- the "title" attribute creates a tooltip when you mouseover the marker, but I want something that will be layered on top of the custom image even when you're not hovering on top of it. Here's the documentation for the marker class, and none of these attributes seem to help: http://code.google.com/apis/maps/documentation/v3/reference.html#MarkerOptions Thank you . . . . Michael

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• Prolog: using the sort/2 predicate

  - by Øyvind Hauge

  So I'm trying to get rid of the wrapper clause by using the sort library predicate directly inside split. What split does is just generating a list of numbers from a list that looks like this: [1:2,3:2,4:6] ---split-- [1,2,3,2,4,6]. But the generated list contains duplicates, and I don't want that, so I'm using the wrapper to combine split and sort, which then generates the desired result: [1,2,3,4,6]. I'd really like to get rid of the wrapper and just use sort within split, however I keep getting "ERROR: sort/2: Arguments are not sufficiently instantiated." Any ideas? Thanks :) split([],[]). split([H1:H2|T],[H1,H2|NT]) :- split(T,NT). wrapper(L,Processed) :- split(L,L2), sort(L2,Processed).

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• JavaScript array to PHP array then process in PHP and return

  - by Constructor

  Example: javascript: var mycourses=new Array(); mycourses[0]="History"; mycourses[1]="Math"; mycourses[1][0]="Introduction to math"; mycourses[1][1]="Math 2"; mycourses[1][2]="Math 3"; PHP will then run these values through functions (please note values are mostly not strings as in the example above but rather numbers), the functions will return some text which will than be displayed in a form How should I go about doing this? p.s.: I found some similar stuff, but nothing quite like this... as far as I see I will have to use JSON (is there a way to code it from JS automatically - saw this for strings) and AJAX

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• Fastest way to zero out a 2d array in C?

  - by Eddy

  I want to repeatedly zero a large 2d array in C. This is what I do at the moment: for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { array[i][j] = 0; } } I've tried using memset: memset(array, 0, sizeof(array)) But this only works for 1D arrays. When I printf the contents of the 2D array, the first row is zeroes, but then I got a load of random large numbers and it crashes.

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• Methodologies or algorithms for filling in missing data

  - by tbone

  I am dealing with datasets with missing data and need to be able to fill forward, backward, and gaps. So, for example, if I have data from Jan 1, 2000 to Dec 31, 2010, and some days are missing, when a user requests a timespan that begins before, ends after, or encompasses the missing data points, I need to "fill in" these missing values. Is there a proper term to refer to this concept of filling in data? Imputation is one term, don't know if it is "the" term for it though. I presume there are multiple algorithms & methodologies for filling in missing data (use last measured, using median/average/moving average, etc between 2 known numbers, etc. Anyone know the proper term for this problem, any online resources on this topic, or ideally links to open source implementations of some algorithms (C# preferably, but any language would be useful)

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• Unix: millionth number in the serie 2 3 4 6 9 13 19 28 42 63 ... ?

  - by HH

  It takes about minute to achieve 3000 in my comp but I need to know the millionth number in the serie. The definition is recursive so I cannot see any shortcuts except to calculate everything before the millionth number. How can you fast calculate millionth number in the serie? Serie Def n_{i+1} = \floor{ 3/2 * n_{i} } and n_{0}=2. Interestingly, only one site list the serie according to Goolge: this one. Too slow Bash code #!/bin/bash function serie { n=$( echo "3/2*$n" | bc -l | tr '\n' ' ' | sed -e 's@\\@@g' -e 's@ @@g' ); # bc gives \ at very large numbers, sed-tr for it n=$( echo $n/1 | bc ) #DUMMY FLOOR func } n=2 nth=1 while [ true ]; #$nth -lt 500 ]; do serie $n # n gets new value in the function throught global value echo $nth $n nth=$( echo $nth + 1 | bc ) #n++ done

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• Real life usage of the projective plane theory

  - by Elazar Leibovich

  I'm learning about the theory of the projective plane. Very generally speaking, it is an extension of the plane, which includes additional points which are defined as the intersection points of two parallel lines. In the projective plane, every two lines have an interesection point. Whether they're parallel or not. Every point in the projective plane can be represented by three numbers (you actually need less than that, but nevemind now). Is there any real life application which uses the projective plane? I can think that, for instance, a software which needs to find the intersections of a line, can benefit from always having an intersection point which might lead to simpler code, but is it really used?

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• C# Convert negative int to 11 bits

  - by Klemenko

  I need to convert numbers in interval [–1024, 1016]. I'm converting to 11 bits like that: string s = Convert.ToString(value, 2); //Convert to binary in a string int[] bits = s.PadLeft(11, '0') // Add 0's from left .Select(c => int.Parse(c.ToString())) // convert each char to int .ToArray(); // Convert IEnumerable from select to Array This works perfectly for signed integers [0, 1016]. But for negative integers I get 32 bits result. Do you have any idea how to convert negative integers to 11 bits array?

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• resetting the image in an NSView

  - by Josan

  I think this is a very simple question, but I’m new to programming so I may be going about it in a wrong-headed way. I have a basic understanding of Objective-C writing terminal applications and am teaching myself how to use the Cocoa GUI. I understand how to use IBOutlet and IBAction to connect a simple button to a method that will repeatedly send random numbers to a textfield . I understand how to add a NSView file, connect it to a custom view in interface builder and draw a path through random points in the view when the application launches. (I’ve been putting this code inside the - (void)drawRect:(NSRect)dirtyRect method that is declared when the file is created). What I can’t seem to figure out is how to connect a button to an action that will then ‘refresh’ the view – in this case repopulate it with another set of random points connected with a path. Looking at the documentation, I think I should somehow be using – (void) setNeedsDisplay(BOOL)flag but nothing I have tried so far had worked. Please tell me, what am I missing here?

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