How to subtract Mean from Matrix along columns

Hi,

In subtraction, there is an example of subtract mean from matrix: A - mean(A) and it works well. But I have a matrix A of 15X1000, and I want to subtract the mean mean(A, 2) along the 1000 columns, how to do that? Thanks Jennifer

Answer 1

[JFz]

With the above help, found that bsxfun works for versions before 2017a:

bsxfun(@minus, A, mean(A, 2))

Answer 2

[KL]

Just the same way, A-A_mean. Here's an example with 5 columns,

>>A = reshape(1:25,5,5) %dummydata

A =

       1     6    11    16    21
       2     7    12    17    22
       3     8    13    18    23
       4     9    14    19    24
       5    10    15    20    25

>>A_mean = mean(A,2)

A_mean =

      11
      12
      13
      14
      15

>>A = A-A_mean

A =

     -10    -5     0     5    10
     -10    -5     0     5    10
     -10    -5     0     5    10
     -10    -5     0     5    10
     -10    -5     0     5    10

EDIT (thanks John)

and for older versions,

 A = bsxfun(@minus,A,A_mean)

[John D'Errico]

+1, but note that this requires a recent release. I think that capability was introduced in R2017a. Otherwise, you will need to use a tool like repmat or bsxfun. It is clear that JFz has a sufficiently recent release, but others might see the post and expect it to work in an old release.

[JFz]

I tried the above but got this error: Error using - Matrix dimensions must agree.

I am using 2016a. I will have to change a lot of code to upgrade to 2017a successfully. Thanks, let me look at repmat and bsxfun.

[JFz]

OK. bsxfun works! bsxfun(@minus, A, mean(A, 2))

Answer 3

[JFz]

Thanks to KL and John! Have a nice day!