efficiently finding the interval with non-zeros in scipy/numpy in Python?

Posted by user248237 on Stack Overflow See other posts from Stack Overflow or by user248237
Published on 2010-04-12T01:25:29Z Indexed on 2010/04/12 1:33 UTC
Read the original article Hit count: 200

Filed under:

python

|

scipy

|

numpy

|

arrays

suppose I have a python list or a python 1-d array (represented in numpy). assume that there is a contiguous stretch of elements how can I find the start and end coordinates (i.e. indices) of the stretch of non-zeros in this list or array? for example,

a = [0, 0, 0, 0, 1, 2, 3, 4]

nonzero_coords(a) should return [4, 7]. for:

b = [1, 2, 3, 4, 0, 0]

nonzero_coords(b) should return [0, 2].

thanks.

© Stack Overflow or respective owner

Related posts about python

unmet dependencies in Ubuntu 12.04

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I tried today to install a dvb-card on my Ubuntu 12.04 (Linux blauhai-linux 3.2.0-25-generic #40-Ubuntu SMP Wed May 23 20:30:51 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux ). The installation failed with an error. After that, i tried to install python (it was already installed but i got this error): linux:~$… >>> More
How can I get sikuli-ide to work?

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I installed sikuli-ide with sudo apt-get install sikuli-ide Everything was fine until I tried to start it from the terminal. I typed sikuli-ide But the only response I got was [info] locale: en_US The application was not started, furthermore there is no desktop file and sikuli-ide does not… >>> More
Getting PATH right for python after MacPorts install

as seen on Super User - Search for 'Super User'
I can't import some python libraries (PIL, psycopg2) that I just installed with MacPorts. I looked through these forums, and tried to adjust my PATH variable in $HOME/.bash_profile in order to fix this but it did not work. I added the location of PIL and psycopg2 to PATH. I know that Terminal is… >>> More
call python with system() in R to run a python script emulating the python console

as seen on Stack Overflow - Search for 'Stack Overflow'
I want to pass a chunk of Python code to Python in R with something like system('python ...'), and I'm wondering if there is an easy way to emulate the python console in this case. For example, suppose the code is "print 'hello world'", how can I get the output like this in R? >>> print… >>> More
Python - Calling a non python program from python?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am currently struggling to call a non python program from a python script. I have a ~1000 files that when passed through this C++ program will generate ~1000 outputs. Each output file must have a distinct name. The command I wish to run is of the form: program_name -input -output -o1 -o2… >>> More

Related posts about scipy

Cocoa App with Python extension which use Scipy -> ImportError: No module named scipy

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi: I have installed Scipy (via macports) for Python on my Mac and it runs fine when running Python scripts. But now I'm using Scipy (via PyObjc) for calculations embedded in a Cocoa App frontend. The following error occurs: ImportError: No module named scipy I am using the "Python.framework" in… >>> More
Mac 10.6 Universal Binary scipy: cephes/specfun "_aswfa_" symbol not found

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi folks, I can't get scipy to function in 32 bit mode when compiled as a i386/x86_64 universal binary, and executed on my 64 bit 10.6.2 MacPro1,1. My python setup With the help of this answer, I built a 32/64 bit intel universal binary of python 2.6.4 with the intention of using the arch command… >>> More
Calculate Matrix Rank using scipy

as seen on Stack Overflow - Search for 'Stack Overflow'
I'd like to calculate the mathematical rank of a matrix using scipy. The most obvious function numpy.rank calculates the dimension of an array (ie. scalars have dimension 0, vectors 1, matrices 2, etc...). I am aware that the numpy.linalg.lstsq module has this capability, but I was wondering if such… >>> More
Vectorizatoin of index operation for a scipy.sparse matrix

as seen on Stack Overflow - Search for 'Stack Overflow'
The following code runs too slowly even though everything seems to be vectorized. from numpy import * from scipy.sparse import * n = 100000; i = xrange(n); j = xrange(n); data = ones(n); A=csr_matrix((data,(i,j))); x = A[i,j] The problem seems to be that the indexing operation is implemented… >>> More
Python to MATLAB: exporting list of strings using scipy.io

as seen on Stack Overflow - Search for 'Stack Overflow'
I am trying to export a list of text strings from Python to MATLAB using scipy.io. I would like to use scipy.io because my desired .mat file should include both numerical matrices (which I learned to do here) and text cell arrays. I tried: import scipy.io my_list = ['abc', 'def', 'ghi'] scipy.io… >>> More