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

Why can't you use makecpt to generate from -75 to +75 with steps of 25, and then use awk to multiply the positive values by two?


On Jan 14, 2014, at 6:17 AM, basem elsaka wrote:

> 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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> <symmetric_scale.jpg><symmetric_scale_2.jpg>

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