[ADMB Users] extraction of array elements using selection logic

[dave fournier]

> I'm looking for an ADMB form of  R-style logical selection from arrays.
> Ignore if this should be regarded as just a C programming question and
> shouldn't be here.
>
> I currently use a bulky loop-based method to accomplish this, looking
> for something more efficient. For example say I have a matrix BEFORE of
> index and value columns and I want to remove rows with values of zero to
> obtain matrix AFTER. Anybody know how to do this in a few lines without
> looping?
>
> 	BEFORE			AFTER
> 1 	34.58641 		1 	34.58641 	
> 2 	0 		3 	42.54367 	
> 3 	42.54367 		4 	46.27856 	
> 4 	46.27856 		5 	49.85982 	
> 5 	49.85982 		6 	53.29379 	
> 6 	53.29379 		7 	56.58652 	
> 7 	56.58652 		8 	59.74382 	
> 8 	59.74382 		9 	62.77126 	
> 9 	62.77126 		10 	65.67418 	
> 10 	65.67418 				
You could write a little function to do this.
If it is to be generic you need to tell it which column to use
something like

    dmatrix N = not_equal(M,2,0.0);