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More than once now I have needed to generate all possible pairs of two vectors in MATLAB which I do with for loops which take up a fair few lines of code i.e.
vec1 = 1:4; vec2 = 1:3; i = 0; pairs = zeros([4*3 2]); for val1 = vec1 for val2 = vec2 i = i + 1; pairs(i,1) = val1; pairs(i,2) = val2; end end Generates ...
1 1 1 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3 4 1 4 2 4 3 There must be a better way to do this which is more MATLAB'esque?
n.b. nchoosek does not do the reversed pairs which is what I need (i.e. 2 1 as well as 1 2), I can't just reverse and append the nchoosek output because the symmetric pairs will be included twice.
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C = combntns( v , k ) returns all possible combinations of the set of values v , given combinations of length k .
b = nchoosek( n , k ) returns the binomial coefficient of n and k , defined as n!/(k!( n - k)!) . This is the number of combinations of n items taken k at a time. C = nchoosek( v , k ) returns a matrix containing all possible combinations of the elements of vector v taken k at a time.
Generate All Combinations of Vectors Using the combvec Function. This example shows how to generate a matrix that contains all combinations of two matrices, a1 and a2 . Create the two input matrices, a1 and a2 . Then call the combvec function to generate all possible combinations.
You can create a vector both by enclosing the elements in square brackets like v=[1 2 3 4 5] or using commas, like v=[1,2,3,4,5]. They mean the very same: a vector (matrix) of 1 row and 5 columns. It is up to you.
Try
[p,q] = meshgrid(vec1, vec2); pairs = [p(:) q(:)]; See the MESHGRID documentation. Although this is not exactly what that function is for, but if you squint at it funny, what you are asking for is exactly what it does.
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You may use
a = 1:4; b = 1:3; result = combvec(a,b); result = result' If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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