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Re: Adding extra white in middle of colour bar [message #85607 is a reply to message #85606]

Wed, 21 August 2013 06:33

Sir Loin Steak
Messages: 42
Registered: January 2012

Member

On Wednesday, 21 August 2013 14:03:57 UTC+1, David Fanning wrote:
> ljs15@fsmail.net writes:
>
>
>
>> I am plotting data that range from negative to positive, so am using a blue-white-red colour bar. However, I would like there to be more white in the middle of the bar.
>
>>
>
>> At the moment I'm using the following clumsy commands to achieve this:
>
>>
>
>> maxv = 10
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>> cgloadct, 13, /brewer, /reverse, ncolors=9, bottom=0, /silent, clip=[0,225]
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>> cgloadct, 16, /brewer, ncolors=9, bottom=12, /silent, clip=[0,225]
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>> clev = scale_vector(findgen(21), -maxv, maxv)
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>> ccol = bindgen(21)
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>> ;Make middle levels white
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>> ccol[9:11] = cgcolor('white')
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>>
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>> and then:
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>>
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>> cgColorbar, ncolors=20, range=[-maxv, maxv]
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>>
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>> While this gives me the plot shading I want, the colour bar is incorrect. As I have manually altered the middle values to white, they don't show in the colour bar, which only uses the 18 colours defined by cgloadct.
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>>
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>> Is there a simple way around this?
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>
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> I think the simplest way around it is this:
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>
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> cgLoadCT, 22, /Brewer, /Reverse, NColors=20
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> cgColorBar, NColors=20, range=[-10,10]
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>
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> Cheers,
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>
>
> David
>
>
>
> --
>
> David Fanning, Ph.D.
>
> Fanning Software Consulting, Inc.
>
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")

Hi David,

That's the method I originally used, but that means the white colour is only being given to the middle contour range.

What I want (for example) is eight contours -10,-9,...,-2 to be shades of blue, and eight contours 2,3,...,10 to be shades of red, and the contours between -2 and +2 to be white.

Not sure if this is possible without having to manually make a colour table and load it with tvlct.

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[Message index]

		Adding extra white in middle of colour bar By: Sir Loin Steak on Wed, 21 August 2013 03:20
		Re: Adding extra white in middle of colour bar By: David Fanning on Wed, 21 August 2013 06:03
		Re: Adding extra white in middle of colour bar By: Sir Loin Steak on Wed, 21 August 2013 06:33
		Re: Adding extra white in middle of colour bar By: David Fanning on Wed, 21 August 2013 07:04
		Re: Adding extra white in middle of colour bar By: Sir Loin Steak on Wed, 21 August 2013 12:52
		Re: Adding extra white in middle of colour bar By: David Fanning on Wed, 21 August 2013 17:13
		Re: Adding extra white in middle of colour bar By: Sir Loin Steak on Thu, 22 August 2013 05:57
		Re: Adding extra white in middle of colour bar By: David Fanning on Thu, 22 August 2013 06:15

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