# [racket] How to iterate through the arrays in a matrix?

 From: Alexander D. Knauth (alexander at knauth.org) Date: Fri Nov 28 17:10:01 EST 2014 Previous message: [racket] How to iterate through the arrays in a matrix? Next message: [racket] How to iterate through the arrays in a matrix? Messages sorted by: [date] [thread] [subject] [author]

```Would something like this work?:
(matrix-map-rows
(lambda (row)
(matrix- row arr))
final-data-matrix)

http://docs.racket-lang.org/math/matrix_poly.html?q=matrix%20row%20map#%28def._%28%28lib._math%2Fmatrix..rkt%29._matrix-map-rows%29%29

On Nov 28, 2014, at 4:56 PM, Animesh Pandey <animeshpandey.etno at gmail.com> wrote:

> (map
>  (λ(i)
>    (matrix-
>     (list->matrix 1 4 i)
>     (list->matrix 1 4 arr)))
>  final-data)
>
> I used this method where final-data is a list of lists and I iterate through each list, convert it to a matrix and then subtract a pre-defined constant list to it. What I really need is a way to iterate through a matrix and not a list of lists as I have do to a lot of matrix operations.
>
>
> On Fri, Nov 28, 2014 at 4:41 PM, Animesh Pandey <animeshpandey.etno at gmail.com> wrote:
> Hi,
> I have a 80 X 4 matrix. I have iterate through each row and subtract each row with another array at each iteration. At first I thought to convert all array to list and do all the operations and then again convert the final list if lists to a matrix. But I somehow think that is not a suited way. I tried using "for*/matrix" but could not get it right. Could any one give an example on how to iterate a matrix (array for arrays)?
>
> My matrix looks like this:
> > (list*->matrix final-data)
> (array
>  #[#[5.1 3.5 1.4 0.2]
>    #[4.9 3.0 1.4 0.2]
>    #[4.7 3.2 1.3 0.2]
>    #[4.6 3.1 1.5 0.2]
>    #[5.0 3.6 1.4 0.2]
>    #[5.4 3.9 1.7 0.4]
>    #[4.6 3.4 1.4 0.3]
>    #[5.0 3.4 1.5 0.2]
>    #[4.4 2.9 1.4 0.2]
>    #[4.9 3.1 1.5 0.1]
> ...........
>
> Thanks!
>
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