Mean of the third dimension

Hi I an new to matlab and learning thru practice and patience. I have a data set with for precipitation containing data for 37 years. X=141, Y=41 and T=37. I want to get the mean per year (37) I tried the following code but on my dataset I ended uo with 71 observations. Why this is happening? If I only want the mean per year? Thanks in advance.

avg3=nanmean(rain(:,:,3));

Answer 1

[John D'Errico]

Not entirely sure what you are asking.

Do you want to compute the mean for each year for each combination of X and Y? That would result in a 141x41 array.

MeanRain = mean(rain,3);

Do you want to compute the mean over all X and Y, resulting in one element per year, so a vector of length 37? Here, I'd just reshape the rain matrix to be a 141*41 by 37 array, so 2-dimensional. Then take the mean down the columns of that array, so on the first dimension. The result of the computation below would be a 1x37 vector.

MeanRain = mean(reshape(rain,[],37),1);

Either could be what you are asking.

[desert_scientist90]

Sorry if I was not clear enough. My goal is to achieve one mean ( point) per year. In total I want 37 averages one per year. After that I want to calculate the zscore per year to be able to do a time series.

[John D'Errico]

Then you just use the second option I gave.

Answer 2

[TADA]

try this:

avgPerYear = nanmean(rain, [1,2]);

that would generate an inconvenient 3rd dimention vector

so you can reshape it into a row\column vector:

avgPerYear = reshape(nanmean(rain, [1,2]), size(rain,3), 1, 1); % column vector output
avgPerYear = reshape(nanmean(rain, [1,2]), 1, size(rain,3), 1); % row vector output