[GRASS-dev] matplotlib example script

[Glynn Clements]

Yann Chemin wrote:

> this happens because the data has NAN (see r.info output):
>  Range of data:    min = nan  max = nan
> 
> Is there a way to discard NAN in a.min() and a.max() calculations?
> Or is there a NAN-resistant mode in matplotlib?

NaN should never appear in GRASS rasters. When it does, it's a bug in
the module which created the map (do you know which module was
responsible in this case?).

One of the things which is on my to-do list for 7.x is to change
G_is_[fd]_null_value() to treat *all* NaN values as null (currently,
it checks for a specific bit pattern, which is just one possible NaN
value).

Once that is done, then r.stats' -n flag will prevent NaNs from making
it into the output.

In the meantime, you can clean up maps which contain NaNs with e.g.:

	r.mapcalc 'newmap = if(oldmap == oldmap,oldmap,null())'

or, with recent versions of r.null:

	r.null map setnull=nan

-- 
Glynn Clements <glynn at gclements.plus.com>