[Gretl-devel] $coeff misbehavior

[Allin Cottrell]

On Tue, 11 Mar 2008, Stefano Balietti wrote:

> I tried to access the single values of the $coeff array directly with the
> command
> 
> a = $coeff[x,1]
> 
> that is a usage of the $coeff array not mentioned in the command 
> reference, but anyway it is supposed to return a scalar. On the 
> contrary it returns a matrix 1x1.

It now returns a scalar unless you force the issue by saying

matrix a = $coeff[x,1]

> i could specify the new variable as scalar
> 
> scalar a = $coeff[x,1]
> 
> but here another inconvenient raises. If I try to print the variable a
> without explicitly using the print command, after a few runnig of the same
> script gretl crashes...

Thanks for the example.  Fixed in CVS.

> By the way it could be nice to access the coefficients in the 
> array with a command like $coeff( number), useful if you don't 
> know the name of the variables.

The documentation seems to have slipped a little on this point; 
I'll try to fix that soon.  But here's the deal:

$coeff(foo) : with round parentheses we require the name of a
parameter.

$coeff[k] : with square brackets we select a coefficient by number 
(position in the array)

If you want to get the coefficient of a certain variable whose ID 
number in the dataset you know, but whose name you don't know
(and whose position in the array you don't know -- though that 
seems a bit weird):

  string vname = varname(ID)
  scalar b = $coeff(@vname)

In (very) current CVS you could omit the '@':

  scalar b = $coeff(vname)

It would be preferable if you could do

  scalar b = $coeff(varname(ID))

but strings are not yet sufficiently tightly integrated in 
genr.

Allin.