Re: [Help-gsl] Wrong result in vector from gsl_vector_alloc_col_from_matrix

[Stephan Petzchen]

Hi Peter,

thanks for your reply.



Here is my code:

uint coffset=4;

/// 1 1 1 1 1 1 1
/// 2 2 2 2 2 2 2
/// 3 3 3 3 3 3 3
/// 4 4 4 4 4 4 4
gsl_matrix* m=gsl_matrix_calloc(4,7);

for(int i=0;i < m->rows; i++)
for(int j=0;j < m->columns; j++)
m->data[i * m->tda + j]=i+1;

//Expected:
/// x x x x 1 x x
/// x x x x 2 x x
/// x x x x 3 x x
/// x x x x 3 x x
gsl_vector* v = gsl_vector_alloc_col_from_matrix(m,coffset);

/// But GSL gives:
/// x x x x 1 1 1
/// 1 x x x x x x
/// x x x x x x x
/// x x x x x x x
for(int i=0;i < v->size; i++)
Assert.AreEqual(m->data[i * m->tda + coffset],v->data[i]);
gsl_vector_free(v);
gsl_matrix_free(m);

Same issue with: gsl_matrix_column, gsl_matrix_diagonal, so probably my
expectation and/or understanding is wrong.

I appreciate your reply.

best,
Stephan

On Wed, Nov 14, 2012 at 7:16 AM, Peter Johansson <troj...@gmail.com> wrote:

> On 11/14/2012 03:41 AM, Stephan Petzchen wrote:
>
>> Hi,
>>
>> I am working on the 1.15 version of GSL and get a wrong result in vector v
>> from gsl_vector_alloc_col_from_**matrix.  (matrix/gsl_vector_double.h,
>> matrix/getset_source.c)
>>
>> My understanding is that it should return the matrix column data for a
>> specified column. So, with gsl_vector_alloc_row_from_**matrix, here the
>> specified row will be returned.
>>
>> Example:
>>
>> Matrix:
>> 1 1 1 1 1 1 1
>> 2 2 2 2 2 2 2
>> 3 3 3 3 3 3 3
>> 4 4 4 4 4 4 4
>>
>> Expected result for column offset 4 with vector size 4 (specified by no.
>> of
>> matrix rows): 1 2 3 4
>> x x x x 1 x x
>> x x x x 2 x x
>> x x x x 3 x x
>> x x x x 4 x x
>>
>> Actual result:
>> x x x x 1 1 1
>> 2 x x x x x x
>> x x x x x x x
>> x x x x x x x
>>
>>  I can not reproduce this. It would help if you please could post your
> code, output, and expected output.
>
> Cheers,
> Peter
>