matlab - how to vectorize array reformatting? -

i have .csv file data on each line in format (x,y,z,t,f), f value of function @ location (x,y,z) @ time t. each new line in .csv gives new set of coordinates (x,y,z,t), accompanying value f. .csv not sorted.

i want use imagesc create video of data in xy-plane, time progresses. way i've done reformatting m more usable imagesc. i'm doing 3 nested loops, this

m = csvread('file.csv'); uniquex = unique(m(:,1)); uniquey = unique(m(:,2)); uniquet = unique(m(:,4));  m_reformatted = zeros(length(uniquex), length(uniquey), length(uniquet));  = 1:length(uniquex)     j = 1:length(uniquey)         k = 1:length(uniquet)             m_reformatted(i,j,k) = m( ...                 m(:,1)==uniquex(i) & ...                 m(:,2)==uniquey(j) & ...                 m(:,4)==uniquet(k), ...                 5 ...             );          end      end end 

once have m_reformatted, can loop through timesteps k , use imagesc on m_reformatted(:,:,k). doing above nested loops slow. possible vectorize above? if so, outline of approach helpful.

edit: noted in answers/comments below, made mistake in there several possible z-values, haven't taken account. if single z-value, above ok.

this vectorized solution allows negative values of x , y , many times faster non-vectorized solution (close 20x times test case @ bottom).

the idea sort x, y, , t values in lexicographical order using sortrows , using reshape build time slices of m_reformatted.

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the code:

idx = find(m(:,3)==0);            %// find rows z==0 m2 = m(idx,:);                    %// m2 has rows z==0 m2(:,3) = [];                     %// delete z coordinate in m2 m2(:,[1 2 3]) = m2(:,[3 1 2]);    %// change (x,y,t,f) (t,x,y,f)  m2 = sortrows(m2);                 %// sort rows t, x, y  numt = numel(unique(m2(:,1)));     %// number of unique t values numx = numel(unique(m2(:,2)));     %// number of unique x values numy = numel(unique(m2(:,3)));     %// number of unique y values  %// fill time slice matrix data m_reformatted = reshape(m2(:,4), numy, numx, numt); 

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note: assuming y refers columns of image , x refers rows. if want these flipped, use m_reformatted = permute(m_reformatted,[2 1 3]) @ end of code.

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the test case used m (to compare result other solutions) has nxnxn space t times slices:

n = 10; t = 10;  [x,y,z]     = meshgrid(-n:n,-n:n,-n:n); numpoints   = numel(x); x=x(:); y=y(:); z=z(:); s = repmat([x,y,z],t,1); t = repmat(1:t,numpoints,1); m = [s, t(:), rand(numpoints*t,1)]; m = m( randperm(size(m,1)), : );