# how can propagate error for division of two matrices?

조회 수: 1(최근 30일)
Joseph 13 Jun 2018
Commented: Joseph 19 Jul 2018
I have two arrays E(i,j,k) and E_2(i,j,k) in which some elements of these matrices are nan values. while, I can calculate standard deviations S(i,j) = nanstd(E(i,j,:)); and S_2(i,j) = nanstd(E_2(i,j,:)); for E and E_3, i don't know howe to calculate standard deviation for E_2(i,j,k)./E(i,j,k). i was wondering if it is possible using propegation of error (function sigma = PropError(f,varlist,vals,errs)) or any other way.

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### 채택된 답변

Arvind Narayanan 6 Jul 2018
Hi Joseph,
If the second matrix(E(i,j,k) in this case) has all non zero elements(NaN allowed), then only we can calculate standard deviation of this p./q type matrix. Otherwise, the resulting matrix will have Inf in it which would result in standard deviation in NaN .
Since Inf makes the mean and other central tendencies of the matrix non-quantifiable, the result is NaN.
For matrix with non-zero elements, we can use p./q and then use nanstd to find standard deviation.
Hope this helps,
Arvind

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Joseph 19 Jul 2018
These two matrices are measurements with the known error for each element. lets say for matrix E(i,j,k) there is an error(i,j,k) matrix. and same for E_2 matrix. I didn't mention this in my question.

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