Re: [Gretl-devel] Improvements in the user-defined function packages
On Thu, 18 Oct 2007, andreas.rosenblad(a)ltv.se wrote:
Currently, when writing a user-defined function, the parameters
can be of six types: bool (scalar variable acting as a Boolean
switch), int (scalar variable acting as an integer), scalar
(scalar variable), series (data series), list (named list of
series) and matrix (named matrix or vector).
To make it easier to write a user-defined function and make it
more flexible I would appreciate if three other parameter types
could be included:
* "discrete" (a data series with only discrete values)
* "proportion" or "quantile" (a scalar which value is between 0 and
1)
* "select" (providing a list of alternatives to select from).
As it is now, the first two parameter types, "discrete" and
"proportion", could be input to the function as "series" and
"scalar", and the user has to let the function check if they are
discrete or between 0 and 1. It would be nice if it instead was
automatically checked already at the input by the parameter type
chosen.
"proportion" would be quite easy to do; "discrete" less so. The
trouble is that I don't think "discrete" denotes a well-defined
data type. It would, I suppose, if we restricted it to integer
values, but some people think that's too restrictive. As things
stand, I think it's up to the function writer to decide what
counts as discrete in any given context.
For the third parameter type, "select", I imagine writing
e.g.
function(select rejectionregion["two sided","one sided
lower","one sided upper"]) would in the GUI produce a drop-down
list for this parameter
That's definitely a nice idea. We could have a go at that after
the 1.6.6 release.
Allin.