[GRASS-user] r.colors

[Micha Silver]

On 28/03/2013 14:54, Nathan Barber - NOAA Federal wrote:
> Background
>
> We generate a precipitation graphic that is based on the mean of an 
> ensemble of models.  Because it goes out 16 days, we can have a wide 
> variety of amounts...sometimes it can be as little as 2 inches other 
> times it can be as great as 6 or 7.  This variability can cause some 
> issues with users when our color scale always changes relative to the 
> amounts.  For example Day 1, 1 inch is yellow and 3 inches is 
> purple....Day 2, 2 inches is yellow and 6 inches is purple.
>
> Is there a way to categorize amounts, say 0-1, 1-2, 2-3, 4-5, 5-6, 7+ 
> so that purple will always represent 7+ and yellow will always be 0-1, 
> etc...I've looked at the r.colors wiki page but I can't seem to get 
> the rules to work correctly.  I need a consistent color scheme for the 
> graphic that communicates the level of concern properly to the user.
>
> Any examples would be greatly appreciated...Thanks.
>

Sure, just create a single rules file (say "standard_precip_colors.txt" 
)of the format:
1 yellow
3 orange
5 red
7 blue
100% purple
end

Now apply this rules file to each new precipitation raster with
r.colors map=<new raster> rules=standard_precip_colors.txt

HTH


> -- 
> Nathan Barber
> Hydrologist
> NOAA National Weather Service
> Ohio River Forecast Center <http://www.erh.noaa.gov/ohrfc/>
> 1901 S State Rt 134
> Wilmington, OH  45177
> (937) 383-0528
>
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-- 
Micha Silver
GIS Consulting
052-3665918
http://www.surfaces.co.il