histutils.h File Reference

HW: Histogram utilities for converting ROOT histograms to numpy arrays for use in Python. More...

#include "TH1.h"
#include "TH2.h"
#include "TH2Poly.h"
#include <pybind11/numpy.h>

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Typedefs
using	HistTuple = std::tuple< py::array_t< M3::float_t >, py::array_t< M3::float_t >, py::array_t< M3::float_t > >

Functions
void	FillEdgesPointer (py::array_t< M3::float_t > edges_buf, TAxis *axis, int nbins)
HistTuple	THNToNumpy (std::unique_ptr< TH1 > &hist)
py::tuple	HistToNumpy (std::unique_ptr< TH1 > &hist)

Detailed Description

HW: Histogram utilities for converting ROOT histograms to numpy arrays for use in Python.

Author

Henry Wallace

Ewan Miller

Definition in file histutils.h.

Typedef Documentation

HistTuple

using HistTuple = std::tuple<py::array_t<M3::float_t>, py::array_t<M3::float_t>, py::array_t<M3::float_t> >

Definition at line 16 of file histutils.h.

Function Documentation

FillEdgesPointer()

void FillEdgesPointer	(	py::array_t< M3::float_t >	edges_buf,
		TAxis *	axis,
		int	nbins
	)

Definition at line 18 of file histutils.h.

                                                                              {
    auto edges_ptr = static_cast<M3::float_t*>(edges_buf.request().ptr);
    for (int i = 0; i <= nbins; ++i) {
        edges_ptr[i] = axis->GetBinLowEdge(i + 1);
    }
    edges_ptr[nbins] = axis->GetBinLowEdge(nbins + 1) + axis->GetBinWidth(nbins + 1);
}

HistToNumpy()

py::tuple HistToNumpy ( std::unique_ptr< TH1 > &  hist )

inline

Definition at line 56 of file histutils.h.

{
    if(dynamic_cast<TH2Poly*>(hist.get())){
        throw std::runtime_error("TH2Poly is not supported for conversion to numpy arrays");
    }
 
    return py::cast(THNToNumpy(hist));
}

THNToNumpy()

HistTuple THNToNumpy

(

std::unique_ptr< TH1 > &

hist

)

Definition at line 26 of file histutils.h.

                                              {
    int nbinsX = hist->GetNbinsX();
    
    
    py::array_t<M3::float_t> edgesX(nbinsX + 1);
    FillEdgesPointer(edgesX, hist->GetXaxis(), nbinsX);
    
    py::array_t<M3::float_t> edgesY;
    
    // If we need to get the contents as a 2D array, we need to check if the histogram is actually 2D
    int nbinsY = hist->GetNbinsY();
    if(nbinsY > 1){
        edgesY = py::array_t<M3::float_t>(nbinsY + 1);
        FillEdgesPointer(edgesY, hist->GetYaxis(), nbinsY);
    }
 
    // Now we fill the contents
    py::array_t<M3::float_t> contents({nbinsY, nbinsX});
    auto contents_buf = contents.request();
    M3::float_t* contents_ptr = static_cast<M3::float_t*>(contents_buf.ptr);
 
    for(int iy=0; iy<nbinsY; ++iy){
        for(int ix=0; ix<nbinsX; ++ix){
            contents_ptr[iy * nbinsX + ix] = hist->GetBinContent(ix + 1, iy + 1);
        }
    }
 
    return std::make_tuple(contents, edgesX, edgesY);
}