Extracting and summing data from a 3d matrix
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Hi there,
I have some data in a 3d matrix 11*32*19. I want to a) identify all columns where there is a non-NaN and b) identify the blocks of non-NaNs (from 1 row long to 11 rowns long) and sum together the blocks in each of the 32 columns, giving a total value for each column against the column name for all the 19 'pages' combined. I have some code to do that for a 2d matrix (below), although i am just realising that it will miss the blocks that start at row 1 :/ so any suggestions on that front would be awesome too.
filename = '1001_1_2';
[locAll,typeAll]=find(isfinite(mVocs)); %extracting the locations of all the non NaNs (finite numbers)
indVocsAll=any(isfinite(mVocs));
colindx = find(indVocsAll==1);
colres = zeros(length(colindx),1);
for i =1:length(colindx)
tmpdat = mVocs(:,colindx(i));
blocklength = zeros(length(tmpdat),1);
for fi = 1:length(tmpdat)-1
if isnan(tmpdat(fi)) && ~isnan(tmpdat(fi+1)) %finding where the column goes from NaN to 1
count = fi+1;
count2 = 1;
while ~isnan(tmpdat(count)) %also count Non-Na
count = count+1;
count2 = count2+1;
end
%tmpdat2 = tmpdat(fi+1:fi+count2-1);
blocklength(fi) = count2;
end
end
blocklength = nonzeros(blocklength);
savename = strcat(savedir, 'filename.mat');
save(savename, 'blocklength');
colres(i) = length(blocklength);
colres(:,2) = colindx;
end
by counting the start of the number of blocks in each column - i am just realising that it will miss the blocks that start at row 1 :/ so any suggestions on that front would be awesome too.
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回答 (1 件)
Nipun
2023 年 9 月 27 日
Hi Emu,
I understand that you have a three dimensional matrix with dimensions: 11,32,19 with few NaN values. And, you are trying to get a sum-block output against each column which has a non-NaN value. I assume that the output will be a 32 x 19 matrix with one summation for each column across all rows.
In the example code below, I have generated a random matrix with the required dimensions. Please refer to the documentation for sum function in MATLAB for any clarifications.
M = rand(11,32,19);
% Generate 100 random indices to make them nan
idx = [];
for i=1:12000
x = randi(size(M,1),1);
y = randi(size(M,2),1);
z = randi(size(M,3),1);
idx = [idx [x,y,z]];
M(x,y,z) = NaN;
end
% sum over all rows for each column across all 'pages' (3rd dimension)
A = sum(M,1,"omitnan");
size(A)
Hope this helps.
Regards,
Nipun
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