Re: Fwd: How to make a non-symmetric color pallet around zero

Hallo Shahar,
I have the same problem like you. I'm trying to make symmetric colorbar from
non-symmetric color scale
As you can see in the attached map, I'm trying to plot from -75 to zero
every 25 spacing and from 0 to 150 every 50. My target is from -75 to 150
only 6 spacing (3 negative and 3 positive).
There are mainly three problems:
1- as mentioned (symmetric spacing issue)
2- how to play with -B option in psscale to be -B25 and -B50 at the same
time ?? is there an option in psscale that is similar to -T in makecpt?
3- how to make continuous colorbar in makecpt after appending the file with
-N option? Because as you see nobody can distinguish between negative and
positive values.
Of course writing the following will lead to another color series (see 2nd
attachment)

makecpt -Z -Chaxby -T-75.0/0.0/25.0  -N > paletteTwice.cpt
 makecpt -Z -Crainbow -T0.0/150.0/50.0 >> paletteTwice.cpt

So did you or anyone succeed to solve this problem. Anyone has suggestions,
pleeeeez

Basem
Institute of Geodesy and Geoinformation, Bonn, Germany
Currently: KACST, Saudi Arabia


-----Original Message-----
From: World-Wide GMT Usage and Help Mailing List
[mailto:[email protected]] On Behalf Of Paul Wessel
Sent: 08 January, 2014 2:14 AM
To: [email protected]
Subject: [Bulk] Re: [GMT-HELP] Fwd: How to make a non-symmetric color pallet
around zero

In GMT5 see makecpt's new option -G for selecting just part of an incoming
cpt range.  You can then run makecpt twice; first for the negative values
and you stretch those via your -Tmin/0/inc and then append the positive side
stretched with -T0/max/inc, using -N during the first call.
in GMT4 you'll need to do some awking.

-p

On Jan 7, 2014, at 12:53 PM, Shahar Barak <[email protected]> wrote:

> Hi,
> 
> I'm trying to plot a figure that shows velocity perturbations by color 
> (results of seismic tomography). I want values at zero and around zero 
> to be white, but I don't want the color pallet to be symmetric. The 
> minimum and maximum values are different.
> In order to force white to be around zero I use grd2cpt with the -T 
> option, however this forces the color pallet to be symmetric.
> Any ideas on how to accomplish this? I need it to be automated, i.e, 
> not by manually editing the CPT file.
> 
> Thanks,
> 
> Shahar
> 
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