[GRASS-dev] r.series counting maps over certain threshold?

[Glynn Clements]

Markus Neteler wrote:

> The existing implementation has been reverted last year, but how to
> do that now? I have to find out at which DOY in a pixel a certain value
> has been reached. Input are all single daily GDD maps of the year. So
> far I used r.series with threshold and count.
> 
> Another usage scenario: count all days over a certain temperature pixelwise...
> ?

At present, the only solution is to pre-process the maps with
r.mapcalc then run r.series on the processed maps.

Alternatively, you could re-implement the threshold= option, but
without breaking the quantile= option (which is the reason why the
original version was reverted).

Also, you might consider changing the c_thresh() method to be more
generally useful; I can't imagine that the current implementation
would be of use for anything other than the exact case for which it
was originally written; e.g. it won't help with your second example
because it's triggered by an in-range test (with a hard-coded range of
threshold +/- 10) rather than a greater-than test.

Another option would be to just use r.mapcalc (using a script to
generate the expression). AFAIK, r.mapcalc doesn't have any hard-coded
limits on the number of input maps or the complexity of the
expression; the memory consumption will be worse than r.series (each
intermediate result will get its own row buffer), but only by a
constant factor.

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