class TPaveStats: public TPaveText

The histogram statistics painter class

A PaveStats is a PaveText to draw histogram statistics and fit parameters.

Statistics Display

The type of information shown in the histogram statistics box can be selected with:

      gStyle->SetOptStat(mode);

The "mode" has up to nine digits that can be set to on(1 or 2), off(0).

      mode = iourmen  (default = 000001111)
      k = 1;  kurtosis printed
      k = 2;  kurtosis and kurtosis error printed
      s = 1;  skewness printed
      s = 2;  skewness and skewness error printed
      i = 1;  integral of bins printed
      o = 1;  number of overflows printed
      u = 1;  number of underflows printed
      r = 1;  rms printed
      r = 2;  rms and rms error printed
      m = 1;  mean value printed
      m = 2;  mean and mean error values printed
      e = 1;  number of entries printed
      n = 1;  name of histogram is printed

For example:

      gStyle->SetOptStat(11);

displays only the name of histogram and the number of entries, whereas:

      gStyle->SetOptStat(1101);

displays the name of histogram, mean value and RMS.

WARNING 1: never do:

      gStyle->SetOptStat(000111);

but instead do:

      gStyle->SetOptStat(1111);

because 0001111 will be taken as an octal number!

WARNING 2: for backward compatibility with older versions

      gStyle->SetOptStat(1);

is taken as:

      gStyle->SetOptStat(1111)

To print only the name of the histogram do:

      gStyle->SetOptStat(1000000001);

NOTE that in case of 2D histograms, when selecting only underflow (10000) or overflow (100000), the statistics box will show all combinations of underflow/overflows and not just one single number.

The parameter mode can be any combination of the letters kKsSiourRmMen

      k :  kurtosis printed
      K :  kurtosis and kurtosis error printed
      s :  skewness printed
      S :  skewness and skewness error printed
      i :  integral of bins printed
      o :  number of overflows printed
      u :  number of underflows printed
      r :  rms printed
      R :  rms and rms error printed
      m :  mean value printed
      M :  mean value mean error values printed
      e :  number of entries printed
      n :  name of histogram is printed

For example, to print only name of histogram and number of entries do:

      gStyle->SetOptStat("ne");

To print only the name of the histogram do:

      gStyle->SetOptStat("n");

The default value is:

      gStyle->SetOptStat("nemr");

When a histogram is painted, a TPaveStats object is created and added to the list of functions of the histogram. If a TPaveStats object already exists in the histogram list of functions, the existing object is just updated with the current histogram parameters.

Once a histogram is painted, the statistics box can be accessed using h->FindObject("stats"). In the command line it is enough to do:

      Root > h->Draw()
      Root > TPaveStats *st = (TPaveStats*)h->FindObject("stats")

because after h->Draw() the histogram is automatically painted. But in a script file the painting should be forced using gPad->Update() in order to make sure the statistics box is created:

      h->Draw();
      gPad->Update();
      TPaveStats *st = (TPaveStats*)h->FindObject("stats");

Without gPad->Update() the line h->FindObject("stats") returns a null pointer.

When a histogram is drawn with the option "SAME", the statistics box is not drawn. To force the statistics box drawing with the option "SAME", the option "SAMES" must be used. If the new statistics box hides the previous statistics box, one can change its position with these lines ("h" being the pointer to the histogram):

      Root > TPaveStats *st = (TPaveStats*)h->FindObject("stats")
      Root > st->SetX1NDC(newx1); //new x start position
      Root > st->SetX2NDC(newx2); //new x end position

To change the type of information for an histogram with an existing TPaveStats one should do:

      st->SetOptStat(mode);

Where "mode" has the same meaning than when calling gStyle->SetOptStat(mode) (see above).

One can delete the statistics box for a histogram TH1* h with:

      h->SetStats(0)

and activate it again with:

      h->SetStats(1).

Fit Statistics

The type of information about fit parameters printed in the histogram statistics box can be selected via the parameter mode. The parameter mode can be = pcev (default = 0111)

      p = 1;  print Probability
      c = 1;  print Chisquare/Number of degrees of freedom
      e = 1;  print errors (if e=1, v must be 1)
      v = 1;  print name/values of parameters

Example:

      gStyle->SetOptFit(1011);

print fit probability, parameter names/values and errors.

1. When "v" = 1 is specified, only the non-fixed parameters are shown.
2. When "v" = 2 all parameters are shown.

Note: gStyle->SetOptFit(1) means "default value", so it is equivalent to gStyle->SetOptFit(111)