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From Ted Dunning <>
Subject Re: [math] RealMatrix.set(double)
Date Mon, 22 Aug 2011 20:38:38 GMT
On Mon, Aug 22, 2011 at 1:27 PM, Phil Steitz <> wrote:

> I think it would be good to add this, but it would probably be
> better to give it a different name.  What name, I am not sure.
> Maybe setAll or fill.  Might also be useful to have versions that
> fill submatrics.

Mahout allows this via overloading of an assign method.
 Matrix.assign(double) over-writes all cells with a constant value.
 Matrix.assign(Matrix) copies data into the target.  x.assign(Matrix y,
BinaryFunction f) does element-wise x_ij = f(x_ij, y_ij)

> Here is a little joke to lighten things up a bit.  What if we just
> allow people to specify negative indices to mean "everything."  So
> for example, setEntry(-1, -1, 0) sets all entries to 0, setEntry(1,
> -1, 0) sets the first row to 0.  Just kidding ;)

Can be useful.

I find the TCL convention more useful where -1 refers to the last element of
a vector.

This sort of thing does tend to freak out the more mathematically inclined
and it does make it harder to catch errors in mathematical code since it
mutes indexing errors.

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