Need algorithm to create the list

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Fayyaz
Fayyaz 2014-7-6
评论： Fayyaz 2014-7-6
Hello,
I need to create a matrix of order 1614006*3, The sequence should be
1st Col (origin) , 2nd Col (Destination) , 3rd Col (Survey_Location)
Origin (1) Destination(1) Survey_Location(1)
Origin (1) Destination(1) Survey_Location(2)
.......
Origin (1) Destination(1) Survey_Location(246)
Origin (1) Destination(2) Survey_Location(1)
...........
Origin (1) Destination(81) Survey_Location(246)
......
Origin (2) Destination(1) Survey_Location(1)
.........
Origin (81) Destination(81) Survey_Location(246)
For this case rows should be 81*81*246=1614006
  2 个评论
Fayyaz
Fayyaz 2014-7-6
Hello, it is not different from the previous question. I just posted this question in a more clear way. I am going to delete the previous question.
Thanks.

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采纳的回答

Image Analyst
Image Analyst 2014-7-6
编辑：Image Analyst 2014-7-6
I'm sure there's a more clever vectorized way - Andrei can probably do it in a single line! - but there's always the brute force way:
Origin = randi(9, [81, 1]);
Destination = randi(9, [81, 1]);
Survey_Location = randi(9, [246, 1]);
numOutputRows = size(Origin, 1) * size(Destination, 1) * size(Survey_Location, 1)
output = zeros(numOutputRows, 3);
tic;
row = 1;
for r1 = 1 : size(Origin, 1)
for r2 = 1 : size(Destination, 1)
for r3 = 1 : size(Survey_Location, 1)
output(row, :) = [Origin(r1), Destination(r2), Survey_Location(r3)];
row = row + 1;
end
end
end
toc
Takes 1.4 second on my computer.
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Image Analyst
Image Analyst 2014-7-6
Oh, I thought you already had some arrays so I just used sample arrays. If you want sequential arrays, you can do
Origin = (1:81)';
Destination = (1:81)';
Survey_Location = (1:246)';
Fayyaz
Fayyaz 2014-7-6
Perfect! Actually I am not that much familiar with MATLAB, but I hope I will be able to understand quite soon. Thanks again.

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更多回答（2 个）

Andrei Bobrov
Andrei Bobrov 2014-7-6
[z,y,x] = ndgrid(Survey_Location,Destination,Origin);
out = [x(:),y(:),z(:)];
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Image Analyst
Image Analyst 2014-7-6
Aha! I knew Andrei could do it in a line or two. He's the master of that.
Fayyaz
Fayyaz 2014-7-6
Ya I've realized when Andrei did this.
@Andrei, if possible, kindly look into this question too, you've almost solved it.
http://www.mathworks.com/matlabcentral/answers/140325-matrix-creation-code-problem#answer_143883

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Cedric
Cedric 2014-7-6
编辑：Cedric 2014-7-6
Hello Muhammad,
Here is an example, with 3 elements Origin and Destination, and a 4 elements Survey_Location..
% - Dummy test case.
Origin = 10 : 12 ;
Destination = 100 : 102 ;
Survey_Location = [500, 600, 700, 800] ;
% - Define columns of final array and concatenate.
c1 = reshape( repmat( Origin(:)', 3*4, 1 ), [], 1 ) ;
c2 = repmat( reshape( repmat( Destination(:)', 4, 1 ), [], 1 ), 3, 1 ) ;
c3 = repmat( Survey_Location(:), 3*3, 1 ) ;
X = [c1, c2, c3] ;
Running this, you get
>> X
X =
10 100 500
10 100 600
10 100 700
10 100 800
10 101 500
10 101 600
10 101 700
10 101 800
10 102 500
10 102 600
10 102 700
10 102 800
11 100 500
11 100 600
11 100 700
11 100 800
11 101 500
11 101 600
11 101 700
11 101 800
11 102 500
11 102 600
11 102 700
11 102 800
12 100 500
12 100 600
12 100 700
12 100 800
12 101 500
12 101 600
12 101 700
12 101 800
12 102 500
12 102 600
12 102 700
12 102 800
EDIT : for your case, you want to replace 3 by 81, and 4 by 246.

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