21 views (last 30 days)

I am trying to create a matrix from two vectors (i.e. A = [0:2] and B = [-2:2]) where the values for each cell of the matrix is a function of the indices. I cannot see the path to get it there, any simple examples I can follow?

Thanks

Cedric Wannaz
on 6 Jan 2018

Edited: Cedric Wannaz
on 6 Jan 2018

Not sure that I understand. If you wanted to create a rectangular array whose elements are a the result of some arithmetic operation between corresponding elements of A and B, you could use the fact that MATLAB expands automatically operands of such operations (from 2016b on, otherwise you have to use BSXFUN):

>> A = 0 : 2 ; B = -2 : 2 ;

>> A.' .* B

ans =

0 0 0 0 0

-2 -1 0 1 2

-4 -2 0 2 4

Note that here we first make A a 3x1 column vector by transposition. Then we apply an element-wise operation ( .* ) between this transpose and B that is 1x5, and MATLAB expands automatically A.' along B and vice versa (hence building 3x5 arrays) and performs the operation.

If you needed to apply a function that is not an arithmetic operation, you could do it using BSXFUN (performing an explicit call to a function that does an implicit expansion..):

>> result = bsxfun( @plus, A.', B )

result =

-2 -1 0 1 2

-1 0 1 2 3

0 1 2 3 4

or through an explicit expansion (using REPMAT, REPELEM, or MESHGRID):

>> [Bx, Ax] = meshgrid( B, A )

Bx =

-2 -1 0 1 2

-2 -1 0 1 2

-2 -1 0 1 2

Ax =

0 0 0 0 0

1 1 1 1 1

2 2 2 2 2

applying whatever function to the two arrays:

>> plus( Ax, Bx )

ans =

-2 -1 0 1 2

-1 0 1 2 3

0 1 2 3 4

Cedric Wannaz
on 6 Jan 2018

Opportunities for recent engineering grads.

Apply Today
## 3 Comments

## Direct link to this comment

https://www.mathworks.com/matlabcentral/answers/375904-how-can-i-create-a-matrix-with-the-values-of-the-elements-is-a-function-of-the-indices#comment_522065

⋮## Direct link to this comment

https://www.mathworks.com/matlabcentral/answers/375904-how-can-i-create-a-matrix-with-the-values-of-the-elements-is-a-function-of-the-indices#comment_522065

## Direct link to this comment

https://www.mathworks.com/matlabcentral/answers/375904-how-can-i-create-a-matrix-with-the-values-of-the-elements-is-a-function-of-the-indices#comment_522067

⋮## Direct link to this comment

https://www.mathworks.com/matlabcentral/answers/375904-how-can-i-create-a-matrix-with-the-values-of-the-elements-is-a-function-of-the-indices#comment_522067

## Direct link to this comment

https://www.mathworks.com/matlabcentral/answers/375904-how-can-i-create-a-matrix-with-the-values-of-the-elements-is-a-function-of-the-indices#comment_522080

⋮## Direct link to this comment

https://www.mathworks.com/matlabcentral/answers/375904-how-can-i-create-a-matrix-with-the-values-of-the-elements-is-a-function-of-the-indices#comment_522080

Sign in to comment.