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I have a 3d vector of size 1498x1498x24. I want to calculate the wholes mean of the vector. I have used two method and got two different result. If anyone please explain this part that will be really helpful. I am giving the code and corresponding result.

mean(mmr_timeseries,'all','omitnan')

Using this i got the value 970.8025. Then i used :

mean(mean(mean(mmr_timeseries,'omitnan'),'omitnan'),'omitnan')

In this case I got 884.2371. I think these two lines are equivalent but I got different result. If ant=yone could please explain this part that will be really helpful. Thank you.

Chunru
on 21 Jul 2021

Edited: Chunru
on 21 Jul 2021

A 2-d example (applicable to 3d in principle).

a=[1 2; 3 3; nan 4; nan nan]

% mean of [1 2 3 3 4] after omitting nans

mean(a,'all','omitnan')

% mean for each column (omit nans)

mean(a,'omitnan')

% mean of the above vector , i.e. [2, 3]

mean(mean(a,'omitnan'),'omitnan')

% The following is for 3d (not shown in this example)

mean(mean(mean(a,'omitnan'),'omitnan'),'omitnan')

Jonas
on 21 Jul 2021

the short answer:

your second approach takes mean values of means and the first approach takes the mean value of all elements

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