Basic Layout of Plotting Code

The following example will demonstrate the basic syntax of the interface. Assume you have two histograms called black and white and a ratio called grey.

TH1D* black = new TH1D("black", "", 100, -3, 3);
black->Sumw2();
black->FillRandom("gaus", 10000);
TH1D* white = new TH1D("white", "", 100, -3, 3);
white->Sumw2();
white->FillRandom("gaus", 10000);
TH1D* grey = (TH1D*)black->Clone("grey");
grey->Divide(white);

First create two object arrays for the main plot and the ratio.

TObjArray* main = new TObjArray();
main->Add(black);
main->Add(white);
TObjArray* ratio = new TObjArray();
ratio->Add(grey);

Now we generate legends for this plot:

Legend* l = new Legend(main, "Black Histo\n White Histo\n", "lp lp", "", "l");
Legend* ll = new Legend(l, "ll"); //Copy first legend so that we can place it seperately
TString info = TString("Black and White Histogram\n");
info.Append("Example\n");
TLegend* lInfo =  new Legend(info.Data(), 2);
main->Add(lInfo);

Then we define marker colors and styles. The ones for the ratios will be added after the ones for the main pad.

vector<Color_t> colors = {kBlack, kBlack, kBlack+3};
vector<Style_t> markers = {kFullCircle, kOpenCircle, kFullCircle};
vector<Size_t>  sizes = {2., 2., 2.};

Adjusting the legend position:

Legend::SetPosition(lInfo, 0.2, 0.3, 0.85, 0.75); // static function
Legend::SetPosition(l, 0.43, 0.6, 0.2, 0.32);
ll->SetPosition(0.43, 0.6, 0.05, 0.22); // non-static function

And finally create the Canvasses:

SquarePlot square = SquarePlot(main, "x", "count");
square.SetStyle(colors, markers, sizes);
square.SetMode(Plot::Presentation);
square.SetRanges(3, -3, 400, 0);
square.Draw(TString("Square.pdf"));
main->AddBefore(lInfo, ll); // replace l in main with ll
SingleRatioPlot rat = SingleRatioPlot(main, ratio, "x", "count", "ratio");
rat.SetOffset(2); // determines where the ratio entries start in the style arrays
rat.SetRanges(3, -3, 400, -10, 3.2, 0.5);
rat.Draw(TString("Ratio.pdf"));

Results:

Square Plot

Ratio Plot

RatioPlot

The syntax for a RatioPlot is very similar to that of a SquarePlot:

RatioPlot just_the_ratio = RatioPlot(ratio, "x", "ratio");
just_the_ratio.SetOffset(2);
just_the_ratio.SetRanges(-3, 3, 0.5, 3.2);
just_the_ratio.Draw("just_ratio.png");

Example of Ratio Plot using the grey array from above

HeatMapPlot

The syntax for a HeatMapPlot is also quite similar to that of a SquarePlot. The main difference to a SquarePlot is that the first entry of the array that is to be plotted must be a TH2.

TH2I* heat = new TH2I("heat", "", 20, 1, 20, 20, 1, 20);
for (Int_t binx = 1; binx < 20; binx++){
  for (Int_t biny = 1; biny < 20; biny++){
    heat->SetBinContent(binx, biny, binx + biny + binx*biny);
  }
}
Legend* legend = new Legend("This is a heatmap!\n", 1);
legend->SetPosition(0.2, 0.75, 0.8, 0.87);
TObjArray* heatArray = new TObjArray();
heatArray->Add(heat);
heatArray->Add(legend);
HeatMapPlot heatMap = HeatMapPlot(heatArray, "X", "Y", "Z");
heatMap.SetRanges(0, 20, 0, 20, 1, 1E3);
heatMap.SetPalette(kPastel, kTRUE);
heatMap.SetLog(kFALSE, kFALSE, kTRUE);
heatMap.Draw("heat.png");

Example of a HeatMapPlot

Defining Colors and Color Gradients

Before defining the colors, we define some histograms we can use for testing:

TObjArray* pal = new TObjArray();
TObjArray* indices = new TObjArray();
palette[0] = new TH1I("palette", "", 20, 1, 20);
pal->Add(palette[0]);
for (Int_t bin = 1; bin < palette[0]->GetNbinsX(); bin++){
  palette[0]->SetBinContent(bin, 1);
  palette[0]->SetBinError(bin, 0.00001);
}
for (Int_t hist = 1; hist < 20; hist++){
  palette[hist] = (TH1I*)palette[0]->Clone(Form("palette_%d", hist));
  palette[hist]->Scale(hist+1);
  pal->Add(palette[hist]);
}
indices->Add(palette[0]);
indices->Add(palette[1]);
indices->Add(palette[2]);

Colors can then be defined as follows:

color blue    {0.00, 0.00, 1.00};
color green   {0.00, 1.00, 0.00};
color red     {1.00, 0.00, 0.00};

The ROOT color index of these colors can then be accessed by the index attribute of color:

Color_t index_of_color_blue  = blue.index;
Color_t index_of_color_red   = red.index;
Color_t index_of_color_green = green.index;

This color index can then be used like any other ROOT color index:

vector<Style_t> markersPal (20, kFullCircle);
vector<Size_t>  sizesPal   (20, 3.);
TMarker* marker = new TMarker();
Plot::SetMarkerProperties(marker, blue.index, kFullSquare, 3.);
std::vector<Color_t> RGB_Colors = {blue.index, red.index, green.index};
SquarePlot indices_usage = SquarePlot(indices, "", "");
indices_usage.SetStyle(RGB_Colors, markersPal, sizesPal);
indices_usage.SetRanges(0, 20, 0, 4);
indices_usage.Draw("indices.png");

Example: Usage of user defined colors with color indices

Color gradients can be defined from color points via the ColorGradient class as follows:

vector<color> rgbRainbow = {blue, green, red};
ColorGradient rainbow = ColorGradient(20, rgbRainbow);
vector<Double_t> spacing = {0., 0.8, 1.};
ColorGradient blue_green_somered = ColorGradient(20, rgbRainbow, spacing);

They can be used either directly as the color array or set as the current palette:

vector<Color_t> colors_rainbow = rgb_rainbow.GetGradient();
SquarePlot direct_usage = SquarePlot(pal, "", "");
direct_usage.SetMode(Plot::Presentation);
direct_usage.SetStyle(colors_rainbow, markersPal, sizesPal);
direct_usage.SetRanges(0, 20, 0, 21);
direct_usage.SetOptions("SAME");
direct_usage.Draw("direct.png");
SquarePlot palette_usage = SquarePlot(pal, "", "");
palette_usage.SetRanges(0, 20, 0, 21);
palette_usage.SetPalette(blue_green_somered, kFALSE);
palette_usage.SetOptions("SAME PMC PLC PFC");
palette_usage.Draw("palette.png");

Example: Usage of user defined palette colors_rainbow via color vector

Example: Usage of user defined palette blue_green_somered via ColorGradient

Legend Usage

Generate a legend from a TObjArray:

TLegend* lIndices = new Legend(indices, "First Histogram\n Second\n and Third", "lp lp lp", "", 3,"indices");

indices->Add(lIndices);

Or with dummy markers from a string with marker specifications:

std::string marker_information = Form("%d %d %f \n %d %d %f \n %d %d %f", kBlack, kFullCircle, 3., kBlue+2, kFullSquare, 3., kMagenta+2, kFullDiamond, 4.);
TLegend* lDummyMarkers = new Legend(marker_information.data(), "Black Full Circle\n Blue Full Square\n Magenta Full Diamond", "lp p lp", 3, "lDummyMarkers");
indices->Add(lDummyMarkers);

Or a legend containing information about your plot:

TLegend* lInformation = new Legend("Some information \n about your histograms \n or your data", 3, "lInformation");

indices->Add(lInformation);

Each legend can be placed individually:

Legend::SetPosition(lIndices, 0.45, 0.8, 0.4, 0.55);
Legend::SetPosition(lDummyMarkers, 0.45, 0.8, 0.6, 0.75);
Legend::SetPosition(lInformation, 0.2, 0.21, 0.77, 0.87);

And plotted by adding them to the array:

SquarePlot legends = SquarePlot(indices, "", "");
legends.SetRanges(0, 20, 0, 21);
legends.SetPalette(kAvocado);
legends.SetOptions("SAME PMC PLC PFC");
legends.Draw("legends.png");

Example: Different Methods for defining a legend

Table of Contents

Basic Layout of Plotting Code

RatioPlot

HeatMapPlot

Defining Colors and Color Gradients

Legend Usage