how to calculate deviation for set of values??

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M.Prasanna kumar 2020-2-5

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评论： M.Prasanna kumar 2020-2-16

No of cases = 112; (112*9=1008)

in each case i have 9 obsevations( but there are missing values in between for which matlab treats them as Nan); so total i have an array of 1008*1

i calculted mean of 9 observations for each case. Now i want to calculate deviation of each observation( 9 observations) from the mean of that particular case.

 M = strcat('iva','.xlsx' );  %% read excel file , iva file consists of 1008*1 array
 M1 = xlsread(M);
 mean_iva = zeros(112,1);  %% initialising matrix
 for ii = 1:9:1008
     mean_iva(ii,1)= nanmean(M1(ii:ii+8))  %% calculating mean for each case
 end
 B = mean_iva(mean_iva~=0);  %% MEAN for all 112 cases
 dev = zeros(1008,1);

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Answer 1

Guillaume 2020-2-5

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在 MATLAB Online 中打开

You could do the same thing you've done for the mean, use a for loop.

However, a much simpler way is to reshape your input vector into 112 columns of 9 rows and simply call mean and std, no loop needed:

%M1: vector whose length is a multiple of 9
assert(mod(numel(M1), 9) == 0, 'Length of M1 must be a multiple of 9');
M1 = reshape(M1, 9, []);  %reshape in rows of 9 elements
mean_iva = mean(M1, 1, 'omitnan');  %calculate the mean across the rows
std_iva = std(M1, 0, 1, 'omitnan'); %standard deviation (normalised by N-1) across the rows