Average values with nan value

Hi

I have a matrix with 3 dimentions; i,j,t(time).

I try to calculate mean value for each time step but the matter is we have some nan-values. I have four basins and decide to calculate avrage for each basin seperately. It doesnot work properly

............................................

for t= 1:length(time)

if j>85

U1(t)=nanmean(Uwind,'all')

else if j>65 & j<85

U2(t)=nanmean(Uwind,'all')

else if j>25 & j<65

U3(t)=nanmean(Uwind,'all')

else

U4(t)=nanmean(Uwind,'all')

end

end

end

end

Answer 1

[Antoni Garcia-Herreros]

Not exacty sure what you mean by U1(t). I you want to calculate the mean (excluding NaNs) for each timestep for all i and a specified range of j this should work.

U4=nanmean(Uwind(:,1:25,:),[1,2]);
U3=nanmean(Uwind(:,26:64,:),[1,2]);
U2=nanmean(Uwind(:,65:84,:),[1,2]);
U1=nanmean(Uwind(:,65:end,:),[1,2]);

[Adam Danz]

Instead of nanmean, use mean with the omitnan flag.

M = mean(A,dim,"omitnan")

For example,

U4 = mean(Uwind(:,1:25,:),[1,2],'omitnan');

mean has more capabilities such as supporting tall arrays, GPU arrays, and code generation, works better with tables, etc. nanmean is discouraged starting in MATLAB R2020b.

Answer 2

[Cameron]

myArray = nan(8,1); %array of nan values
indx = 1:2:7; %index to populate that array 
myArray(indx,1) = rand(length(indx),1) %have some nan and some numbers

myArray = 8×1

0.1698 NaN 0.0233 NaN 0.8454 NaN 0.6111 NaN

mean(myArray(~isnan(myArray))) %take the average of only the numbers

ans = 0.4124