For-Loop Alternative for Faster Code Execution

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RDG
RDG 2013-6-27
Suppose,
a{1}=[1 6;
1 9;
1 8;
3 7;
3 0;
4 0;
5 0;
5 0;
5 0;
5 0;]
desired_answer{1}= [1 6;
1 6;
1 6;
3 9;
3 9;
4 8;
5 7;
5 7;
5 7;
5 7;]
Is there a more efficient way I can do this without having to use for loop? (Cell Array is used because it is adapted from my problem)
  2 个评论
Matthew Eicholtz
Matthew Eicholtz 2013-6-27
Can you provide more details? Here is what I conclude from your description: the number of nonzero entries in the second column equals the number of unique values in the first column; then, you want to assign each of the second-column values to all instances of the appropriate first-column value, in order. Is that correct?
RDG
RDG 2013-6-27
The value "6" in column 2 should be assigned to value "1" in column 1, "9" to "3", "8" to "4", "7" to "5".

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采纳的回答

Matthew Eicholtz
Matthew Eicholtz 2013-6-27
Still unsure about your problem setup, but the following code will yield your desired result for the example above.
[~,~,idx] = unique(a{1}(:,1));
a{1}(:,2) = a{1}(idx,2);

更多回答（1 个）

Matthew Eicholtz
Matthew Eicholtz 2013-6-27
And if the for loop you are concerned about is looping through the cells in your cell array, then try this code:
[~,~,idx] = cellfun(@(x) unique(x(:,1)),a,'uni',0);
a = cellfun(@(x,y) [x(:,1) y],a,cellfun(@(z,i) z(i,2) ,a,idx,'uni',0),'uni',0);
Perhaps this is not the most elegant solution, in which case I expect the MATLAB pros will chime in shortly.

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