[GRASS-user] XY trace plots

[Markus Metz]

Hamish wrote:
>
> [...] I've just added an experimental
> module in GRASS addons called r.to.vect.lines.
>
>   http://grass.osgeo.org/wiki/GRASS_AddOns#r.to.vect.lines
>

>
> ps- if any python+ctypes experts want to have a look over it please do...
> especially to fix the G_is_null_value() call which is currently broken.

The argument must be a pointer, try

G_is_null_value(byref(in_rast[col]), data_type)

or
in_val = in_rast[col]
G_is_null_value(byref(in_val), data_type)

Markus M