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# element-wise operations

In MATLAB element-wise operations:

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".*", ".^", "./" and so on.

In SAGE I have only found ".elementwise_product()". Are there any other element-wise operations on matrices, vectors, lists?

Thanks in advance!

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## 1 Answer

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For lists, you can use list comprehension or the map function:

sage: [M[i] + N[i] for i in xrange(len(M))]
sage: map(operator.add, N, M)


For matrices, there is no such mechanism out of the box, but you can make one by yourself as follows:

def elementwise(operator, M, N):
assert(M.parent() == N.parent())
nc, nr = M.ncols(), M.nrows()
A = copy(M.parent().zero_element())
for r in xrange(nr):
for c in xrange(nc):
A[r,c] = operator(M[r,c], N[r,c])
return A


and then use it as follows:

sage: elementwise(operator.add, M, N)
sage: elementwise(operator.pow, M, N)
sage: elementwise(operator.mul, M, N)
sage: elementwise(operator.div, M, N)


and so on.

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## Comments

Orz, so quick. Thanks

( 2013-11-10 14:15:34 +0200 )edit

assert() is perhaps not a good choice for element-wise division? And why do you use xrange(), but not range()?

( 2013-11-11 06:33:44 +0200 )edit

I believe that numpy arrays will do this automatically, however. Sage is built around mathematical constructs, but you can use Numpy from within Sage to do this.

( 2013-11-11 11:25:44 +0200 )edit

Thanks! I am starting to learn NumPy.

( 2013-11-22 11:46:57 +0200 )edit

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Asked: 2013-11-10 12:47:44 +0200

Seen: 3,865 times

Last updated: Nov 10 '13