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Join Date: Oct 2007
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Newbie Poster
this is a small example from the gsl example online
I need to get the value from the "&evec_i.vector " into a 4x4 dimensional array
such that
abc[4][4]= vector elements
how can I do this ? those 16 values will create the 4x4 matrix
I need to get the value from the "&evec_i.vector " into a 4x4 dimensional array
such that
abc[4][4]= vector elements
how can I do this ? those 16 values will create the 4x4 matrix
#include <stdio.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_eigen.h>
int main (void)
{
double data[] = { 1.0 , 1/2.0, 1/3.0, 1/4.0,
1/2.0, 1/3.0, 1/4.0, 1/5.0,
1/3.0, 1/4.0, 1/5.0, 1/6.0,
1/4.0, 1/5.0, 1/6.0, 1/7.0 };
gsl_matrix_view m = gsl_matrix_view_array(data, 4, 4);
gsl_vector *eval = gsl_vector_alloc (4);
gsl_matrix *evec = gsl_matrix_alloc (4, 4);
gsl_eigen_symmv_workspace * w = gsl_eigen_symmv_alloc (4);
gsl_eigen_symmv (&m.matrix, eval, evec, w);
gsl_eigen_symmv_free(w);
gsl_eigen_symmv_sort (eval, evec, GSL_EIGEN_SORT_ABS_ASC);
{
int i;
for (i = 0; i < 4; i++)
{
double eval_i = gsl_vector_get(eval, i);
gsl_vector_view evec_i = gsl_matrix_column(evec, i);
printf("eigenvalue = %g\n", eval_i);
printf("eigenvector = \n");
gsl_vector_fprintf(stdout, &evec_i.vector, "%g");
}
}
return 0;
} Last edited by Ancient Dragon : Oct 18th, 2007 at 8:31 am. Reason: add code tags
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Join Date: Aug 2005
Location: near St Louis, Missouri, USA
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I don't really know, but did you try the obvious ?
for(i = 0; i < 4; ++i)
{
for(j = 0; j < 4; ++j)
{
data[i][j] = gsl_matrix_column(i, j);
}
} •
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Join Date: Oct 2007
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Newbie Poster
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Originally Posted by Ancient Dragon 
I don't really know, but did you try the obvious ?
for(i = 0; i < 4; ++i) { for(j = 0; j < 4; ++j) { data[i][j] = gsl_matrix_column(i, j); } }
It doesnt work, since the function takes argument as below
gsl_matrix_column (gsl_matrix * m, size_t j)
http://www.gnu.org/software/gsl/manu...005fcolumn-947
I got the value of eigenvalue pretty easily but I am having trouble with the eigenvector
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Join Date: Oct 2007
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Newbie Poster
Ancient Dragon:
I did a workaround the problem by printing the output of the vector to a file and then reading them into an array
sure doesnt look impressive :<
I did a workaround the problem by printing the output of the vector to a file and then reading them into an array
sure doesnt look impressive :<
#include <stdio.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_eigen.h>
// trying to take the values of eigenvector and eigenvalues and put it in a array
int main (void)
{
FILE *data3;
data3 = fopen("data3.txt", "w");
if (data3 == NULL)
{
printf("File doesn't exist\n");
exit (EXIT_FAILURE);
}
double data[] = { 1.0 , 1/2.0, 1/3.0, 1/4.0,
1/2.0, 1/3.0, 1/4.0, 1/5.0,
1/3.0, 1/4.0, 1/5.0, 1/6.0,
1/4.0, 1/5.0, 1/6.0, 1/7.0 };
double datax[4][4];
double datay[16];
gsl_matrix_view m = gsl_matrix_view_array (data, 4, 4);
gsl_vector *eval = gsl_vector_alloc (4);
gsl_matrix *evec = gsl_matrix_alloc (4, 4);
gsl_eigen_symmv_workspace * w = gsl_eigen_symmv_alloc (4);
gsl_eigen_symmv (&m.matrix, eval, evec, w);
gsl_eigen_symmv_free (w);
// gsl_vector_fprintf (stdout, evec.vector, "%g");
int i,j,p=0;
for (i = 0; i < 4; i++)
{
double eval_i = gsl_vector_get (eval, i);
gsl_vector_view evec_i = gsl_matrix_column (evec, i);
printf ("eigenvalue = %g\n", eval_i);
printf ("eigenvector = \n");
gsl_vector_fprintf (data3, &evec_i.vector, "%g");
}
gsl_vector_free (eval);
gsl_matrix_free (evec);
fclose(data3);
FILE *fr;
int n;
char line[80];
float abc[10][10];
// int i=0,j=0;
fr = fopen ("data3.txt", "r");
for(i = 0; i < 4; ++i)
{
for(j = 0; j < 4; ++j)
{
fgets(line, 80, fr);
sscanf (line, "%f", &abc[i][j]);
printf ("\n%f", abc[i][j]);
}
}
printf("\n\n");
for(i = 0; i < 4; ++i)
{
for(j = 0; j < 4; ++j)
{
printf ("%f ", abc[i][j]);
}
printf("\n");
}
fclose(fr);
return 0;
}
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Join Date: Nov 2005
Location: Canada
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Posting Whiz in Training
You're looking in the wrong section of the manual. You don't want to create a vector view. Check out this section: http://www.gnu.org/software/gsl/manu...-elements.html
I think that this is what you seek:
I think that this is what you seek:
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double gsl_matrix_get (const gsl_matrix * m, size_t i, size_t j)
This function returns the (i,j)-th element of a matrix m. If i or j lie outside the allowed range of 0 to n1-1 and 0 to n2-1 then the error handler is invoked and 0 is returned. An inline version of this function is used when HAVE_INLINE is defined.
dwk
Seek and ye shall find.
"Only those who will risk going too far can possibly find out how far one can go."
-- TS Eliot.
"I have not failed. I've just found 10,000 ways that won't work."
-- Thomas Alva Edison
"The only real mistake is the one from which we learn nothing."
-- John Powell
Seek and ye shall find.
"Only those who will risk going too far can possibly find out how far one can go."
-- TS Eliot.
"I have not failed. I've just found 10,000 ways that won't work."
-- Thomas Alva Edison
"The only real mistake is the one from which we learn nothing."
-- John Powell
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