Understand the fillmissing function with movmean

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Tiago Dias 2018-3-27

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评论： Tiago Dias 2018-3-28

采纳的回答： Guillaume

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Hi, I would like to ask how the fillmissing movmean method works.

I got A

A = [1 2 5;4 5 7;NaN -1 8;7 6 0];
A1 = fillmissing(A,'movmean',2);
A2 = fillmissing(A,'movmean',3);

A1 turns the NaN into 4, and A2 turns into 5.5.

I tried to open the function fillmissing but wasn't able to find how the calculation is made.

The 4 is the result of a nanmean of (4+NaN)/1 = 4, divided by 1 because it is a nanmean? The 5 is the result of a nanmean of (4+NaN+7)/2 = 11/3 = 5.5? divided by 2 because it is a nanmean?

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Guillaume 2018-3-27

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编辑：Guillaume 2018-3-27

在 MATLAB Online 中打开

The missing elements are in effect calculated with

movmean(A, k, 'omitnan')

with k your windows size.

As per the movmean documentation, when 'omitnan' is specified, the window is reduced as necessary when NaNs are encountered. When k is 2 movmean is normally the mean of the element and the previous one, so when a NaN is encountered the result is just the previous element, hence why you get 4. When k is 3 the |movmean |is the mean of the element and the ones on either side, so when a NaN is encountered the result is just the mean of the neighbouring elements.

edit: the best way to actually understand what is going on is to set a breakpoint at the start of the fillmissing function and step through it after you've called it.