How to carry index within a function?

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Xiaohan Du
Xiaohan Du 2016-11-16
评论： Xiaohan Du 2016-11-16
Hi all,
This is a very long question ;-)
I have a function which sort a grid to cell blocks, the function is:
function [otpt] = GridtoBlock(inpt)
xy = cellfun(@unique, num2cell(inpt, 1), 'UniformOutput', false);
x = xy{1};
y = xy{2};
otpt = cell(numel(y) - 1, numel(x) - 1);
for xidx = 1 : numel(x) - 1
for yidx = 1 : numel(y) - 1
otpt{yidx, xidx} = [repmat(x(xidx:xidx+1), 2, 1), repelem(y(yidx:yidx+1), 2)];
end
end
for i_rte = 1:numel(otpt)
otpt_temp = otpt{i_rte};
otpt{i_rte}(3, :) = otpt_temp(4, :);
otpt{i_rte}(4, :) = otpt_temp(3, :);
end
If the inpt is (a square domain contains 3 by 3 points):
inpt_noindex = [-1 -1; -1 1; 1 -1; 1 1; -1 0; 0 -1; 0 0; 0 1; 1 0];
then the otpt is:
otpt_noindex =
[4x2 double] [4x2 double]
[4x2 double] [4x2 double]
otpt_noindex{:}
ans =
-1 -1
0 -1
0 0
-1 0
ans =
-1 0
0 0
0 1
-1 1
ans =
0 -1
1 -1
1 0
0 0
ans =
0 0
1 0
1 1
0 1
i.e. the function automatically sort the x and y coordinates and put them into a 2 by 2 cell block.
Now my question is, if I find the row index of inpt, i.e.
inpt_index = [1 -1 -1; 2 -1 1; 3 1 -1; 4 1 1; 5 -1 0; 6 0 -1; 7 0 0; 8 0 1; 9 1 0];
How can I modify the function to get the otpt with the original row index? i.e. I want the otpt to be
otpt_index =
[4x3 double]
[4x3 double]
[4x3 double]
[4x3 double]
otpt_index{:}
ans =
1 -1 -1
6 0 -1
7 0 0
5 -1 0
ans =
5 -1 0
7 0 0
8 0 1
2 -1 1
ans =
6 0 -1
3 1 -1
9 1 0
7 0 0
ans =
7 0 0
9 1 0
4 1 1
8 0 1
The goal is to make the row index follows the matrix operation. I have written a for loop using isequal to compare each block against the inpt, but this is not efficient when the inpt becomes large.
Thanks a lot!
  2 个评论
KSSV
KSSV 2016-11-16
for
inpt = [1 -1 -1; 2 -1 1; 3 1 -1; 4 1 1; 5 -1 0; 6 0 -1; 7 0 0; 8 0 1; 9 1 0];
your otpt is of size 2X8 with element as 4x2 double. This you want to change to what size?
Xiaohan Du
Xiaohan Du 2016-11-16
Hi KSSV,
For
inpt_index = [1 -1 -1; 2 -1 1; 3 1 -1; 4 1 1; 5 -1 0; 6 0 -1; 7 0 0; 8 0 1; 9 1 0];
I'd like to have the same sort method, but only 'carry' the original index with the sorted blocks.
If you compare the otpt_index against otpt_noindex, you'll find that otpt_index is the 2nd and 3rd column of otpt_noindex, the only difference between otpt_index and otpt_noindex is the 1st column of otpt_index, which is the original row index from inpt_index.
I hope this is clear.

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