Excluding index in numpy like negative index in R?
Hi I can exclude a list of items by using negative index in R (R-project) ie myarray[-excludeindex]. As negative indexing in numpy (And python) behave differently ,how can I exclude a list of item in numpy? Regards, Teimourpour
You can make a mask array in numpy to prune out items from an array that you don't want, denoting indices you want to keep with 1's and those you don't want to keep with 0's. For instance,
a = np.array([1,3,45,67,123]) mask = np.array([0,1,1,0,1],dtype=np.bool) anew = a[mask]
will set anew equal to array([3, 45, 123])
Josh
On Tue, Dec 9, 2008 at 12:25 PM, Bab Tei babaktei@yahoo.com wrote:
Hi I can exclude a list of items by using negative index in R (R-project) ie myarray[-excludeindex]. As negative indexing in numpy (And python) behave differently ,how can I exclude a list of item in numpy? Regards, Teimourpour
Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
On Tue, Dec 9, 2008 at 12:25 PM, Bab Tei babaktei@yahoo.com wrote:
I can exclude a list of items by using negative index in R (R-project) ie myarray[-excludeindex]. As negative indexing in numpy (And python) behave differently ,how can I exclude a list of item in numpy?
Here's a painful way to do it:
x = np.array([0,1,2,3,4]) excludeindex = [1,3] idx = list(set(range(4)) - set(excludeindex)) x[idx]
array([0, 2])
To make it more painful, you might want to sort idx.
But if excludeindex is True/False, then just use ~excludeindex.
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Bab Tei -
Joshua Lippai -
Keith Goodman