[ROOT] Suggestion for COL(Z) plots

From: Thomas Hadig (hadig@SLAC.stanford.edu)
Date: Tue Nov 26 2002 - 23:10:41 MET


Hi all,

I was just switching from an older version of ROOT (3.00/06) to the newest
3.03/09 and noticed that the color scale on COLZ plots is different: Less
than the 50 colors of the gSystem->SetPalette(1) default are used.

I found the reason for this change to be the introduction of contour levels.
My histograms do not have contour levels set, so the default of 20 levels.

I know you can change in the TH* itself, but this is very inconvenient
for e.g. tree->Draw("...") or TBrowser draw selections as a new histogram
is created each time.

It would be nice to either have that default number configurable 
(e.g. gSystem->SetDefaultNumberContourLevels()) or to change with
the number of colors in the color palette, i.e. change the lines
in THistPainter.cxx  void THistPainter::PaintColorLevels(Option_t *)
from
//                  Initialize the levels on the Z axis
   Int_t ncolors  = gStyle->GetNumberOfColors();
   Int_t ndiv   = fH->GetContour();
   if (ndiv == 0 ) {
      ndiv = 20;
      fH->SetContour(ndiv);
   }
to
//                  Initialize the levels on the Z axis
   Int_t ncolors  = gStyle->GetNumberOfColors();
   Int_t ndiv   = fH->GetContour();
   if (ndiv == 0 ) {
      ndiv = ncolors;
      if (ndiv <= 0 ) ndiv=20;
      fH->SetContour(ndiv);
   }

Ciao
Thomas

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Thomas Hadig            MS 62, 2575 Sand Hill Road, Menlo Park CA 94025, USA
       hadig@slac.stanford.edu                         Tel.: +1 650 926 2810
       http://www.slac.stanford.edu/~hadig/ 
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