Suppose I have a categorical raster map and I want to 'cut out' a subset (with g.region to set a small region and r.mapcalc to create the new map). This map has a smaller number of categories, as is shown using e.g., r.category. However, when plotting the legend, all the categories of the original map are included in the legend. Checking the 'cats' file shows that it indeed lists all original categories and labels, including for those categories not present in the new map. This doesn't make sense to me, but perhaps I am missing something here?
Suppose I have a categorical raster map and I want to 'cut out' a subset
(with g.region to set a small region and r.mapcalc to create the new
map). This map has a smaller number of categories, as is shown using
e.g., r.category. However, when plotting the legend, all the categories
of the original map are included in the legend. Checking the 'cats' file
shows that it indeed lists all original categories and labels, including
for those categories not present in the new map. This doesn't make sense
to me, but perhaps I am missing something here?
AFAIK, the legend is determined by the color table, and the color table is probably just copied as is from the input to the output map. You can check with r.colors.out. If you redefine a color table with only the relevant categories, then the legend should reflect that.
You could also try d.legend with the -n flag to only show categories which have a label.
Suppose I have a categorical raster map and I want to 'cut out' a subset
(with g.region to set a small region and r.mapcalc to create the new
map). This map has a smaller number of categories, as is shown using
e.g., r.category. However, when plotting the legend, all the categories
of the original map are included in the legend. Checking the 'cats' file
shows that it indeed lists all original categories and labels, including
for those categories not present in the new map. This doesn't make sense
to me, but perhaps I am missing something here?
AFAIK, the legend is determined by the color table, and the color table is probably just copied as is from the input to the output map. You can check with r.colors.out. If you redefine a color table with only the relevant categories, then the legend should reflect that.
Hi Moritz, that is what I thought, and as the whole color table does indeed get copied over, I wrote a small script to remove the 'redundant color definitions. However, that did not help, the whole 'old' legend is still showing. I had missed that -n flag, so I'll give that a try. Is there a similar option in ps.map to omit categories without label?
From a more conceptual point of view, is there any reason the whole category table is copied over to the new cats file?
You could also try d.legend with the -n flag to only show categories which have a label.
Suppose I have a categorical raster map and I want to 'cut out' a subset
(with g.region to set a small region and r.mapcalc to create the new
map). This map has a smaller number of categories, as is shown using
e.g., r.category. However, when plotting the legend, all the categories
of the original map are included in the legend. Checking the 'cats' file
shows that it indeed lists all original categories and labels, including
for those categories not present in the new map. This doesn't make sense
to me, but perhaps I am missing something here?
AFAIK, the legend is determined by the color table, and the color
table is probably just copied as is from the input to the output map.
You can check with r.colors.out. If you redefine a color table with
only the relevant categories, then the legend should reflect that.
Hi Moritz, that is what I thought, and as the whole color table does
indeed get copied over, I wrote a small script to remove the 'redundant
color definitions. However, that did not help, the whole 'old' legend is
still showing. I had missed that -n flag, so I'll give that a try. Is
there a similar option in ps.map to omit categories without label?
From a more conceptual point of view, is there any reason the whole
category table is copied over to the new cats file?
Probably not. IIUC, this only happens when you have a formula of the form "new = old".
An easy work around:
r.category new | r.category new rules=-
The resulting cats file only contains the cats actually present and you can thus use d.legend -n to only show those.
On Thu, Sep 17, 2015 at 11:56 AM, Moritz Lennert <
mlennert@club.worldonline.be> wrote:
On 16/09/15 10:48, Paulo van Breugel wrote:
On 16-09-15 09:49, Moritz Lennert wrote:
On 15/09/15 20:08, Paulo van Breugel wrote:
Suppose I have a categorical raster map and I want to 'cut out' a subset
(with g.region to set a small region and r.mapcalc to create the new
map). This map has a smaller number of categories, as is shown using
e.g., r.category. However, when plotting the legend, all the categories
of the original map are included in the legend. Checking the 'cats' file
shows that it indeed lists all original categories and labels, including
for those categories not present in the new map. This doesn't make sense
to me, but perhaps I am missing something here?
AFAIK, the legend is determined by the color table, and the color
table is probably just copied as is from the input to the output map.
You can check with r.colors.out. If you redefine a color table with
only the relevant categories, then the legend should reflect that.
Hi Moritz, that is what I thought, and as the whole color table does
indeed get copied over, I wrote a small script to remove the 'redundant
color definitions. However, that did not help, the whole 'old' legend is
still showing. I had missed that -n flag, so I'll give that a try. Is
there a similar option in ps.map to omit categories without label?
From a more conceptual point of view, is there any reason the whole
category table is copied over to the new cats file?
Probably not. IIUC, this only happens when you have a formula of the form
"new = old".
An easy work around:
r.category new | r.category new rules=-
The resulting cats file only contains the cats actually present and you
can thus use d.legend -n to only show those.