\addtogroup tutorial_hist
@{ A histogram is a visual representation of the distribution of quantitative data. TH1 class introduces the basic data structure used in root for histograms.
In a nutshell:
// Open the file to write the histogram to
auto outFile = std::unique_ptr<TFile>(TFile::Open("outfile.root", "RECREATE"));
// Create the histogram object
// There are several constructors you can use (\see TH1). In this example we use the
// simplest one, accepting a number of bins and a range.
int nBins = 30;
double rangeMin = 0.0;
double rangeMax = 10.0;
TH1D histogram("histogram", "My first ROOT histogram", nBins, rangeMin, rangeMax);
// Fill the histogram. In this simple example we use a fake set of data.
// The 'D' in TH1D stands for 'double', so we fill the histogram with doubles.
// In general you should prefer TH1D over TH1F unless you have a very specific reason
// to do otherwise.
const std::array values{1, 2, 3, 3, 3, 4, 3, 2, 1, 0};
for (double val : values) {
histogram.Fill(val);
}
// Write the histogram to `outFile`.
outFile->WriteObject(&histogram, histogram.GetName());
// When the TFile goes out of scope it will close itself and write its contents to disk.
Explore the examples below for different histogram classes
- [Introduction](\ref hist_intro)
- [TH1 Histograms](\ref th1)
- [TH2 Histograms](\ref th2)
- [THnSparse](\ref thnsparse)
- [THStack](\ref thstack)
- [TRatio plots](\ref ratioplots)
- [TPoly](\ref tpoly)
- [Graphics](\ref hist_graphics)
- [TExec](\ref texec)
[List of all tutorials](\ref hist_alltutorials) \anchor hist_intro
| Tutorial | Description |
|---|---|
| hist000_TH1_first.C | First example. |
\anchor th1
These examples shows some of the ratioplots
| Tutorial | Description | |
|---|---|---|
| hist000_TH1_first.C | Hello World example for TH1. | |
| hist001_TH1_fillrandom.C | hist001_TH1_fillrandom.py | Fill a 1D histogram with random values using predefined functions. |
| hist002_TH1_fillrandom_userfunc.C | Fill a 1D histogram from a user-defined parametric function. | |
| hist003_TH1_draw.C | Draw a 1D histogram to a canva. | |
| hist004_TH1_labels.C | 1D histograms with alphanumeric labels. | |
| hist005_TH1_palettecolor.C | Palette coloring for TH1. | |
| hist006_TH1_bar_charts.C | Draw 1D histograms as bar charts. | |
| hist007_TH1_liveupdate.C | hist007_TH1_liveupdate.py | Histograms filled and drawn in a loop. |
| hist008_TH1_zoom.C | Change the range of an axis in a Histogram. | |
| hist009_TH1_normalize.C | Normalizing a Histogram. | |
| hist010_TH1_two_scales.C | hist010_TH1_two_scales.py | Draw two histograms on one canva using different y-axis scales. |
| hist011_TH1_legend_autoplaced.C | Automatic placing of the legend. | |
| hist012_TH1_hksimple.C | Dynamic filling of TH1K histograms. | |
| hist013_TH1_rebin.C | Create a variable bin-width histogram and change bin sizes. | |
| hist014_TH1_cumulative.C | Illustrate use of the TH1::GetCumulative method. | |
| hist015_TH1_read_and_draw.C | hist015_TH1_read_and_draw.py | Read a 1D histogram from a ROOT File and draw it. |
| hist016_TH1_different_scales_canvas.C | Draw two histograms on one canva using different y-axis scales. | |
| hist017_TH1_smooth.C | Histogram smoothing. | |
| hist060_TH1_stats.C | Edit statistics box. | |
| hist061_TH1_timeonaxis.C | Use a time axis as an x axis. | |
| hist062_TH1_timeonaxis2.C | Use a time axis as an x axis and use a time offset. | |
| hist063_TH1_seism.C | Use a time axis as an x axis to show sine signal as a strip chart. | |
| hist101_TH1_autobinning.C | Fill multiple histograms with different functions and automatic binning. |
\anchor th2
| Tutorial | Description |
|---|---|
| hist018_TH2_cutg.C | Use TCutG object to select bins for drawing a region of a 2D histogram. |
| hist019_TH2_projection.C | Display a histogram and its two projections. |
| hist020_TH2_draw.C | Display 2D histogram drawing options. |
| hist021_TH2_reverse_axis.C | Histogram with reverse axis. |
| hist022_TH2_palette.C | Automatic placing of a color palette via option COLZ. |
| hist102_TH2_contour_list.C | Get contours from a 2D histogram. |
\anchor thstack
| Tutorial | Description |
|---|---|
| hist103_THnSparse_hist.C | Evaluate the performance of THnSparse vs TH1/2/3/n. |
\anchor thnsparse
| Tutorial | Description |
|---|---|
| hist023_THStack_simple.C | Stack histograms with class THStack. |
| hist024_THStack_pads.C | Draw stack histograms on subpads. |
| hist025_THStack_2d_palette_color.C | Display multiple 2D histograms picking colors within palette 1. |
| hist026_THStack_color_scheme.C | Use accessible color schemes with THStack. |
| hist027_THStack_palette_color.C | Display multiple 1D histograms picking colors within palette kOcean. |
| hist028_THStack_multicolor.C | Use a THStack to show a 2D histogram with cells with different colors. |
\anchor ratioplots
| Tutorial | Description | |
|---|---|---|
| hist029_TRatioPlot_simple.C | hist029_TRatioPlot_simple.py | Create a simple ratio plot of two histograms using the pois division option. |
| hist030_TRatioPlot_residual.C | hist030_TRatioPlot_residual.py | Create a fit residual plot. |
| hist031_TRatioPlot_residual_fit.C | hist031_TRatioPlot_residual_fit.py | Create a fit residual plot and set the y-axis range for it. |
| hist032_TRatioPlot_fit_lines.C | hist032_TRatioPlot_fit_lines.py | Set custom dashed lines specified by a vector of floats. |
| hist033_TRatioPlot_fit_confidence.C | hist033_TRatioPlot_fit_confidence.py | Set the colors of the confidence interval bands by using |
| hist034_TRatioPlot_fit_margin.C | hist034_TRatioPlot_fit_margin.py | Create a fit residual plot, where the separation margin has been set to 0. |
\anchor tpoly
| Tutorial | Description |
|---|---|
| hist037_TH2Poly_boxes.C | Create a histogram with polygonal bins (TH2Poly). |
| hist038_TH2Poly_honeycomb.C | Create a histogram with hexagonal bins (TH2Poly). |
| hist039_TH2Poly_usa.C | Create a histogram with polygonal bins (TH2Poly). The initial data represent the USA map. |
| hist040_TH2Poly_europe.C | Create a histogram with polygonal bins (TH2Poly). The initial data represent the Europe map. |
| hist041_TProfile2Poly_realistic.C | Create a histogram with polygonal bins representing different particle charges in a detectior. |
| hist042_TProfile2Poly_module_error.C | Create a histogram with polygonal bins simulating a faulty detector panel w.r.t. particle charge. |
| hist056_TPolyMarker_contour.C | Make a contour plot and get the first contour in a TPolyMarker. |
| hist104_TH2Poly_fibonacci.C | Create a histogram representing the "Fibonacci spiral". |
\anchor hist_graphics
| Tutorial | Description |
|---|---|
| hist043_Graphics_highlight.C | Use the highlight mechanism to update the title of a histogram in real time. |
| hist044_Graphics_highlight2D.C | Use the highlight mechanism to displaying the X and Y projections at a bin in real time. |
| hist045_Graphics_highlight_ntuple.C | Use the highlight mechanism to display which events of an ntuple contribute to a bin. |
| hist046_Graphics_highlight1D.C | Use the highlight mechanism to zoom on a histogram. |
| hist047_Graphics_candle_decay.C | Candle plot illustrating a time development of a certain value. |
| hist048_Graphics_candle_hist.C | Illustrate candle plot options. |
| hist049_Graphics_candle_plot.C | Create a candle plot with 2-D histograms. |
| hist050_Graphics_candle_plot_options.C | Illustrate more candle plot options. |
| hist051_Graphics_candle_plot_stack.C | Create a THStack with candle plot option. |
| hist052_Graphics_candle_plot_whiskers.C | Create a candle plot showing the whiskers definition. |
| hist053_Graphics_candle_scaled.C | Illustrate what scaling effects on candle and violin charts. |
\anchor texec
| Tutorial | Description | |
|---|---|---|
| hist057_TExec_th1.C | Echo object at mouse position. | |
| hist058_TExec_th2.C | Echo object at mouse position and show a graphics line. | |
| hist105_TExec_dynamic_slice.C | hist105_TExec_dynamic_slice.py | Show the slice of a TH2 following the mouse position. |
\anchor hist_alltutorials
@}