Matlab to Python ( dot product and dot divide equivalents )

Question

fadams18 2018-11-13

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/429657-matlab-to-python-dot-product-and-dot-divide-equivalents

回答： Fernando Feijoo 2020-2-24

I am converting my matlab funtion to python. I want to rewrite this simple functions in python

function [ H ] = update_H( X , W , H )
H = H.*((W'*X)./secu_plus(W'*W*H,eps));
end
function [ W ] = update_W( X , W , H )
W = W.*((X*H')./secu_plus(W*(H*H'),eps));
end

Note: secu_plus is another function so ignore.

As you may see there are 2 kinds of multiplication * and .*, Also I have ./

so what are the equivalent forms in python [(.* ) (./ ) and (*) ]

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Answer 1

M 2018-11-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/429657-matlab-to-python-dot-product-and-dot-divide-equivalents#answer_346921

Please refer to:

http://mathesaurus.sourceforge.net/matlab-numpy.html

or

https://docs.scipy.org/doc/numpy/user/numpy-for-matlab-users.html

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Answer 2

Fernando Feijoo 2020-2-24

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https://ww2.mathworks.cn/matlabcentral/answers/429657-matlab-to-python-dot-product-and-dot-divide-equivalents#answer_417064

在 MATLAB Online 中打开

I think that it's not possible a simple translation to python of the .* because the tratment of the operation is different in matlab and in Python. I hope this code in Python helps you

f=np.array([2,4])
t=np.array([1,2,3,4,5])
def funMatLabMultip(f,t):
    """create an n x m array from 2 vectors of size n and m.
    Resulting rows are the multiplication of each element of the first vector for all the elements of the second vector
    f=np.array([2,4])
    t=np.array([1,2,3,4,5])
    [[ 2  4  6  8 10]
     [ 4  8 12 16 20]]
    """
    if t.size==t.shape[0]:
        k=f[0]*t
        for i in f[1:]:
            j=i*t
            k=np.vstack((k,j))
    else:
        raise Exception('arrays should 1D arrays')
    return k
k=funMatLabMultip(f,t)
print(k)