Splitting a matrix into smaller matrices...

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Doron 2012-2-20

I have a matrix 1000x3 matrix P which can be generated with the following code: (I call the columns of P: X, Y and Z)

P = [];
for X = 0.1:.1:1; 
for Y = 0.01:.01:1;
Z = Y^2 + X;
P = vertcat(P, [X, Y, Z]);
end
end

I now want to create a matrix which contains all of the rows for which X = 0.5, say.

(This will be a 100x3 matrix in this example)

How do I do this?

Many thanks

D Howard

Walter Roberson 2012-2-20

M2 = P( P(:,1) == 0.5, : );

Walter Roberson 2012-2-20

Use unique() more directly.

[PU, PI, PJ] = unique(P(:,1));

PUC = length(PU);

for i = 1 : PUC

Q{i} = P(PJ == i, :);

end

Notice no floating point comparisons were used.

Doron 2012-2-20

Thanks for this tip

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