Need algorithm to create the list

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

[Star Strider]

How does this differ from your earlier question: Survey data Matrix arrangement?

[Fayyaz]

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.

Answer 1

[Image Analyst]

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.

[Fayyaz]

@Image Analyst: I don't know whether it's too heavy or other reason, it takes a lot of time to run, till now it's in running mode (Although I've i-7 computer)

Also, have you created 3 matrices for Origin (81*1), Destination (81*1) and Survey_Location(246*1)??

[Image Analyst]

Yes. I did. I'll edit to add those before the tic. You have a faster computer than me. I'm using an i5 at the moment. You should get it done at least as fast as me. Actually Cedric's method is probably going to be faster, though perhaps a little more cryptic.

[Fayyaz]

@Image Analyst: Now it's working. But there is one small problem.

I have origin and destination values from 1 to 81, and Survey_Location values from 1 to 246.

In the output, I can't find values greater than 10. Probably you've defined the these in other manner.

Kindly define these vectors as a sequence from 1 to 81 (by 1 increment) for Origin and Destination, and 1 to 246 (by 1 increment) for Survey_Location.

Thank you very much.

[Image Analyst]

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]

Perfect! Actually I am not that much familiar with MATLAB, but I hope I will be able to understand quite soon. Thanks again.

Answer 2

[Andrei Bobrov]

[z,y,x] = ndgrid(Survey_Location,Destination,Origin);
out = [x(:),y(:),z(:)];

[Fayyaz]

Thanks Andrei. It has worked very well.

[Image Analyst]

Aha! I knew Andrei could do it in a line or two. He's the master of that.

[Fayyaz]

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

Answer 3

[Cedric]

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.