Problem in GetBinContent

[nab]

Dear developers,

I have multiple root files Mc_1.root, Mc_2.root etc. In each root file I have a histogram name counter. I want to find the number of entries in each file, secondly I want to add all the entries to get total number of entries in all root files. Kindly help me to do this.

Cheers,
Nab

[couet]

In a loop open the file containing this histogram, get it from file, get the number of entries, and cumulate the number of entries in some variable.

[sbinet]

FWIW here is how I’d do it in Go and go-hep/rootio:

package main

import (
	"fmt"
	"log"
	"os"

	"go-hep.org/x/hep/rootio"
)

func main() {
	fnames := os.Args[1:]
	entries := 0.0
	for _, fname := range fnames {
		n, err := process(fname, "rigidity")
		if err != nil {
			log.Fatalf("error processing %q: %v", fname, err)
		}
		fmt.Printf("file %q: %v\n", fname, n)
		entries += n
	}
	fmt.Printf("\n==> total entries: %v\n", entries)
}

func process(fname, name string) (float64, error) {
	f, err := rootio.Open(fname)
	if err != nil {
		return 0, err
	}
	defer f.Close()

	obj, ok := f.Get(name)
	if !ok {
		return 0, fmt.Errorf("file %q has no object called %q", f.Name(), name)
	}

	h, ok := obj.(*rootio.H1F)
	if !ok {
		return 0, fmt.Errorf("object %q is not a TH1F", name)
	}
	return h.Entries(), nil
}

and then:

$> go get go-hep.org/x/hep/rootio
$> go run ./main.go /path/to/*.root
file "f1.root": 900000
file "f2.root": 900000
file "rigidity.root": 900000

==> total entries: 2.7e+06

(I just put 3 times the same file for that exercize)

hth,
-s