[GAP Forum] A question about rank of a matrix

[Sven Reichard]

Dear Rahul,

the expression [A,B] denotes a list with the two entries A and B. GAP
does not understand that you want to write the two matrices next to each
other.

In GAP a matrix is represented as a list of list. The rows of the matrix
you are interested are the concatenations of the corresponding rows of A
and B. So you can define
gap> C := List([1..Length(A)], i -> Concatenation(A[i], B[i]));
and then compute
gap> Rank(C);

Hope this helps.

Sven Reichard
TU Dresden

On 03.03.2017 04:51, Rahul Kitture wrote:
> Dear Experts,
> 
> I had a simple question about rank of matrices over finite fields in GAP.
> 
> Suppose A and B are matrices (over a finite field GF(p)), considered in GAP.
> 
> Assume that A and B have *same number of rows*.
> 
> Then I want to consider the matrix obtained by putting B after A (i.e. the
> matrix [A B]; it has same  number of rows as A; but number of columns is
> (number of columns of A) + (number of columns of B)) and study rank of [A
> B].
> 
> What is the command to do this?
> 
> I did  *gap > RankMat([A,B]); *
> 
> But it was showing error.
> 
> 
> Thanks in advance!
> 
> -Rahul Kitture
> HRI, Allahabad
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