The methods:
double[][] getData();
double[][] getDataRef();
Provide access to the underlying 2D matrix as a copy or a direct reference.
The method:
double getEntry(int, int);
Provides access to an element of the matrix.
So you can do for example:
Array2DRowRealMatrix m = ...;
int cols = m.getColumnDimension();
int rows = m.getRowDimension();
double[][] data = m.getDataRef();
for (int row = 0; row < rows; row++) {
for (int column = 0; column < cols; column++) {
double d = m.getEntry(row, column);
double d2 = data[row][column];
assert d == d2;
}
}
If you need to visit a part of the matrix then you can use the visitor API.
For example to sum a sub-matrix:
int startRow = 2;
int endRow = 5;
int startColumn = 15;
int endColumn = 20;
double sum = m.walkInOptimizedOrder(
new DefaultRealMatrixPreservingVisitor() {
double s = 0;
@Override
public void visit(int row, int column, double value) {
s += value;
}
@Override
public double end() {
return s;
}
}, startRow, endRow, startColumn, endColumn);
You can read about the available operations in the API here:
https://commons.apache.org/proper/commons-math/javadocs/api-3.6.1/index.html
Regards,
Alex
On Tue, 16 Feb 2021 at 09:28, Oscar Bastidas <[email protected]>
wrote:
> Hello,
>
> Would someone please tell me how I can go about converting a 'RealMatrix'
> object to an array? When I just print out the RealMatrix object I get
> something that looks like:
>
>
> Array2DRowRealMatrix{{123},{456},{789}}
>
>
> I would like to be able to selectively cycle through each number
> individually.
>
> Thanks.
>
> Oscar
>
> Oscar Bastidas, Ph.D.
> Postdoctoral Research Associate
> University of Minnesota
>
