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The functions for accessing the elements of a matrix use the same range
checking system as vectors. You can turn off range checking by recompiling
your program with the preprocessor definition
`GSL_RANGE_CHECK_OFF`

.

The elements of the matrix are stored in “C-order”, where the second
index moves continuously through memory. More precisely, the element
accessed by the function `gsl_matrix_get(m,i,j)`

and
`gsl_matrix_set(m,i,j,x)`

is

m->data[i * m->tda + j]

where `tda` is the physical row-length of the matrix.

- Function:
*double***gsl_matrix_get***(const gsl_matrix **`m`, const size_t`i`, const 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 toand 0 to`n1`-1then the error handler is invoked and 0 is returned. An inline version of this function is used when`n2`-1`HAVE_INLINE`

is defined.

- Function:
*void***gsl_matrix_set***(gsl_matrix **`m`, const size_t`i`, const size_t`j`, double`x`) This function sets the value of the

*(i,j)*-th element of a matrix`m`to`x`. If`i`or`j`lies outside the allowed range of 0 toand 0 to`n1`-1then the error handler is invoked. An inline version of this function is used when`n2`-1`HAVE_INLINE`

is defined.

- Function:
*double ****gsl_matrix_ptr***(gsl_matrix **`m`, size_t`i`, size_t`j`) - Function:
*const double ****gsl_matrix_const_ptr***(const gsl_matrix **`m`, size_t`i`, size_t`j`) These functions return a pointer to the

*(i,j)*-th element of a matrix`m`. If`i`or`j`lie outside the allowed range of 0 toand 0 to`n1`-1then the error handler is invoked and a null pointer is returned. Inline versions of these functions are used when`n2`-1`HAVE_INLINE`

is defined.

Next: Initializing matrix elements, Previous: Matrix allocation, Up: Matrices [Index]