Problem with TColorPallete

[Alkass]

Hello!

I want to plot a 3D plot from 3 gaussian distributions. My problem is that I get a strange color map which also fills with the color for “zero” for points that there are no entries.

I have this in my rootlogon

[code] const Int_t NRGBs = 5;

    const Int_t NCont = 255;
    Double_t stops[NRGBs] = { 0.00, 0.34, 0.61, 0.84, 1.00 };

    Double_t red[NRGBs]   = { 0.00, 0.00, 0.87, 1.00, 0.51 };

    Double_t green[NRGBs] = { 0.00, 0.81, 1.00, 0.20, 0.00 };

    Double_t white[NRGBs] = { 0.00, 0., 0.00, 0.0, 0.00 };

    Double_t blue[NRGBs]  = { 0.51, 1.00, 0.12, 0.00, 0.00 };

    TColor::CreateGradientColorTable(NRGBs, stops, red, white, blue, NCont);

    //gStyle->CreateColorGradientTable(NRGBs, stops, red, green, blue, NCont)

    gStyle->SetNumberContours(NCont);
 }[/code]

but what I get looks like the attachment below. How can I force the “empty region” to be white ?

thanks

Alex

[Jet]

Hello,
Since:

For instance:

UInt_t Number = 3; Double_t Red[3] = { 0.0, 1.0, 1.0 }; Double_t Green[3] = { 0.0, 0.0, 1.0 }; Double_t Blue[3] = { 1.0, 0.0, 1.0 }; Double_t Stops[3] = { 0.0, 0.4, 1.0 };

This defines a table in which there are three color end points: RGB = {0, 0, 1}, {1, 0, 0}, and {1, 1, 1} = blue, red, white The first 40% of the table is used to go linearly from blue to red. The remaining 60% of the table is used to go linearly from red to white.
If you define a very short interval such that less than one color fits in it, no colors at all will be allocated. If this occurs for all intervals, ROOT will revert to the default palette.

Seems like you have to read columns instead of rows since the Reds is the array of R data, Greens the one of G data and Blues of B data in RGB space. For example for a White-Black pallette:

(...)  
   Double_t Stops[NRGBs]  =   {1.00,  0.0}; 
   Double_t Reds[NRGBs]    =  { 1.00, 0.0};
   Double_t Greens[NRGBs]  = { 1.00, 0.0};
   Double_t Blues[NRGBs]   =  { 0.00, 1.00};
   TColor::CreateGradientColorTable(NRGBs, stops, Reds, Greens, Blues, NCont);
(...)

So you could manage your issue with:

(...)  
   Double_t Stops[NRGBs]  = {0.,0.5,1.0}; 
   Double_t Reds[NRGBs]    = { 1.00, 1.00, 1.00};
   Double_t Greens[NRGBs]  = { 0.00, 1.00, 0.00};
   Double_t Blues[NRGBs]   = { 0.00, 1.00, 1.00};
   TColor::CreateGradientColorTable(NRGBs, stops, Reds, Greens, Blues, NCont);
(...)

hope it helps.
have fun

Gabriele