How to create a regular data matrix from irregularly sampled XYZ data with different X and Y coordinates

Dear, I am trying to organise my data in a matrix. The data is in the form of XYZ, where X and Y are irregular. For example a data structure like below

X Y Z

2 0 0.38

2 5 0.348

2 25 0.328

3 2 0.319

3 50 0.212

5 10 0.138

5 60 0.11

5 100 0.087

7 5 0.069

7 9 0.4113

7 45 0.3807

7 95 0.3678

9 10 0.3207

9 35 0.1765

15 65 0.1123

15 75 0.0917

15 99 0.0727

15 125 0.0573

15 150 0.3811

I have a number of Y data points for a particular X. X has a different range from Y and both has irregular intervals. I want to organize the data in a matrix, where X may be in column heading, Y may in Row heading and the matrix elements are the Z data. My target is to extract Z data for a particular X value with different Y or a particular Y with different X. Can anyone please help me. Your help is highly appreciated. Thank you so much.

Answer 1

[Geoff]

Well, I might do this:

d = [2.0000         0    0.3800;
     2.0000    5.0000    0.3480;
     2.0000   25.0000    0.3280;
     3.0000    2.0000    0.3190;
     3.0000   50.0000    0.2120;
     5.0000   10.0000    0.1380;
     5.0000   60.0000    0.1100;
     5.0000  100.0000    0.0870;
     7.0000    5.0000    0.0690;
     7.0000    9.0000    0.4113;
     7.0000   45.0000    0.3807;
     7.0000   95.0000    0.3678;
     9.0000   10.0000    0.3207;
     9.0000   35.0000    0.1765;
    15.0000   65.0000    0.1123;
    15.0000   75.0000    0.0917;
    15.0000   99.0000    0.0727;
    15.0000  125.0000    0.0573;
    15.0000  150.0000    0.3811];

X = d(:,1); Y = d(:,2); Z = d(:,3);

Xs = unique(X);
Ys = unique(Y);
Xi = arrayfun( @(x) find(Xs==x), X );
Yi = arrayfun( @(y) find(Ys==y), Y );
Li = Yi + (Xi-1) * numel(Ys);

XYZ = nan(numel(Ys), numel(Xs));
XYZ( Li ) = Z;

That creates a matrix where each column represents a value in Xs and each row represents a value in Ys, and the Z values are injected accordingly using linear indexing.

[Asim Biswas]

This is perfect. I was exactly looking for this. Thank you so so much. I really appreciate your time.

Thank you again. 10% percent helpful.

[Asim Biswas]

sorry, 100% helpful. not 10% (mistake)

Answer 2

[Andrei Bobrov]

[ii,i2,i2] = unique(d(:,1));
[jj,j2,j2] = unique(d(:,2));
out = [[NaN,ii'];[jj,accumarray([j2,i2],d(:,3),[],[],NaN)]]

[Asim Biswas]

Thank you so much. This is perfect and much more straight forward. Thanks again.

I appreciate your response.

[Ted Rogers]

Bloody amazing. Thank you very much!

Answer 3

[Steven]

Going through Andrei's solution, I think it is more clear to use this:

[ii,~,i2] = unique(d(:,1));
[jj,~,j2] = unique(d(:,2));