MATLAB: Error using ‘omitnan’

Question

Hi MATLAB community,

I wrote a code for identify 999999 to substitute to NaN, my purpose is replace NaN to mean of column data,

I tried follow code:

[l,c]=size(matrix) % size (324,25)
for w=1:c
   for q = 1:l
   if matrix(q,w)==999999     
      matrix(q,w) =NaN;       
      matrix(isnan(matrix))= mean(matrix(:,w),'omitnan'); % in the case NaN is present in column 21, it will substitute the element  for mean of all element in column 21
   end
   end
end   

Could help me?

Grateful

Answer 1

Check out nanmean() in the stats & machine learning toolbox.

An alternative that doesn't require any toolboxes:

nanidx = isnan(matrix(:,w)); 
mean(matrix(~nanidx,w)

Update following comments below

To compute the mean of each column of a matrix while ignoring a key value (999999),

% Create fake data
key = 999999; 
matrix = magic(10); 
matrix(randi(100,1,10)) = key; 
% Identify the columns that contain at least one 999999
isKey = matrix == key; 
colIdx = any(isKey,1); 
% Count the number of rows per column that are not 999999
rowCount = sum(~isKey); 
% Temporarily replace 999999 with 0 and calculate the column means
matrixTemp = matrix .* ~isKey; 
colMean = sum(matrixTemp)./rowCount;
% The 2nd block above can be reduced to
%    isKey = matrix == key; 
%    colMean = sum(matrix .* ~isKey)./ sum(~isKey);