I am using nalgebra and I want to modify one matrix by setting it as the columns of another with compatible dimensions, like this:
let zero: T = convert(0.0);
let mut basis = DMatrix::from_element(rows, rank, zero);
// matrix is an input with dimensions rows x cols
for i in 0..location.len()
{
basis.column_mut(i) = matrix.column(location[i]);
}
I have also tried dereferencing both sides of the assignment and looked for an "assign" method of some kind, no luck.
set_column
doesn't work because DMatrix
does not implement DimName
My current work around is this, but I don;t like it one bit:
// Construct basis vectors initialized to 0.
let zero: T = convert(0.0);
let mut basis = DMatrix::from_element(rows, rank, zero);
for i in 0..location.len()
{
// Copy the pivot column from the matrix.
let col = location[i];
for r in 0..matrix.nrows()
{
basis[(r, i)] = matrix[(r, col)];
}
}
I don't know what column_mut
means, what it does, or how it's supposed to work, either. The documentation for it is fairly sparse (nonexistent). I think set_column
does what you're trying to do (perhaps you called it incorrectly?):
use nalgebra::DMatrix;
let rows = 2;
let cols = 3;
let zero = 0.0;
let mut basis = DMatrix::from_element(rows, cols, zero);
let matrix = DMatrix::from_row_slice(rows, cols, &[
1.0, 3.0, 5.0,
2.0, 4.0, 6.0
]);
let location = [1, 0, 2];
for i in 0..location.len() {
basis.set_column(i, &matrix.column(location[i]));
}
(I tweaked your code to be an MWE)