MATLAB: How to write such a loop

loop for

Hello everybody, I have two data vectors: d1 and d2, I have passed them through a segmentation algorithm, and the resulted class indexes are IDX1 and IDX2. Number of members in each segment are segMem1 for d1 and segMem2 for d2. Now I want to assign one index to each component in d1 (and d2), according to segMem1 (and segMem2). Moe specifically, I want to index the 3 first components of d1 as 1 1 1, the two next components as 2 2 , the 2 third components as 1 1 and so on, and at last I want to have 1 1 1 2 2 1 1 3 4 4 for d1. I have written the following code, and it seems to work for indexing d1. But I don't know how to make another loop to generalize this to both d1 and d2?
clear all
close all
clc
% data
d1 = [10 3 44 33 4 16 7 10 22 54]; 
d2 = [3 24 35 12 3 4 7];
IDX1 = [1 2 1 3 4];
IDX2 = [3 1 2 1];
segMem1 = [3 2 2 1 2]; % Determines how many times each index in IDX1 should be repeated.
segMem2 = [2 1 2 2];
%%Now assign indexes to data vector
n = 1;
a = cell(1,length(d1));
      for k = 1:length(segMem1)
          for j = n:segMem1(k)+n-1
              a{j} = IDX1(k);
          end
          n = n+segMem1(k);
      end
Any help would be greatly appreciated.

Best Answer

>> cell2mat(arrayfun(@(x,y) repmat(x,y,1),IDX1,segMem1,'uniform',0).')
ans =
   1
   1
   1
   2
   2
   1
   1
   3
   4
   4
>>
Since Matlab doesn't know about jagged arrays other than by cell array, you'll have to build the pieces and rearrange them into a cell array.
Oh, a spurious thought though I've never tried it; I suppose one could wrap a cellfun call around arrayfun, maybe to process the two cells as you've smushed them together above; otherwise a loop or the cell array.
ADDENDUM
OK, the looping construction works well enough...
>> for i=1:length(IDX)
     idx=IDX{i};
     seg=s{i};
     cell2mat(arrayfun(@(x,y) repmat(x,1,y),idx,seg,'uniform',0))
   end
ans =
   1     1     1     2     2     1     1     3     4     4
ans =
   3     3     1     2     2     1     1
>>
Left as row vectors for more compact display...
Related Question