## Solve an Upper Triangular System

## Usage

    backsolve(r, x, k=ncol(r))

## Arguments

`r` | an upper triangular matrix giving the coefficients for the system to be solved. Values below the diagonal are ignored.
`x` | a matrix whose columns give ``right-hand sides'' for the equations.
`k` | The number or columns of `r` and rows of `x` to use.

## Value

The solution of the triangular system. The result will be a a vector if `x` is a vector and a matrix if `x` is a matrix.

## References

Dongarra, J. J., J. R. Bunch, C. B. Moler and G. W. Stewart (1978). LINPACK Users Guide. Philadelphia: SIAM Publications.

## See Also

`chol`, `qr`, `solve`.

## Examples

    # no examples yet

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