[GRASS-user] logarithmic scale in raster legend

[Veronica Andreo]

Yeah, I also tried that, and of course, I get a nice gradient in the
legend, but then I need to somehow edit tick-marks.
Logarithm of chlorophyll concentration is, from my point of view,
uninformative. I need the actual values.
I just want to change the display of the legend, like making log of x or y
axis in a plot, that you do not change the
values themselves, just rescale the axis for better visualization... but
maybe not (yet) possible in GRASS ;)

Thanks much!
Vero


2014-06-10 7:40 GMT-03:00 Daniel Victoria <daniel.victoria at gmail.com>:

> What if you use r.mapcalc and apply log to your map to make a new one with
> rescaled values?
> On Jun 9, 2014 12:36 PM, "Veronica Andreo" <veroandreo at gmail.com> wrote:
>
>> Hi list!
>>
>> I have these raster maps of chlorophyll concentration (mg/m3) with a lot
>> of very small values (from 0.02 to 1.5) and few high values (between 20 and
>> 100)... I managed to create my own color table to get a good visualization
>> of the variation... but when I display the legend, i loose the color
>> variation in smaller values...
>>
>> Is it possible to create a logarithmic legend or at least determine which
>> tick-marks I'm interested in?? I've tried with "use" parameter in d.legend
>> (which seemed to meet my needs) setting it to: 0.01,0.1,1,10,100, but works
>> only for categories... There's no such a thing in ps.map, either... which
>> would be the right approach? any ideas?
>>
>> Thanks much in advance!
>> Best,
>>
>> Vero
>>
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>
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