TPie with unknown number of slices

ROOT
1

Hi!

I need a root macro that read values from a file and draw a piechart using them.
I don’t know -a priori- the number of slices, which can change from one file to another.

This is what I tried to do:

/*
 * Draw a pie chart from input file. The input file must contain only
 * 2 columns: value + label
 */

void pchart (string input)
{
	string line;
	string label;
	double y;
	size_t point = 0;
	
	TCanvas *c = new TCanvas("c", "TPie", 500, 500);
	TPie *pie = new TPie();
	
	ifstream fileInput (input.c_str());
	while (getline(fileInput, line)) {
		if (line[0] == '#' || line[0] == '\0') continue;
		stringstream(line) >> y >> label;
		
		pie->SetEntryFillColor(point, point);
		pie->SetEntryVal(point, y);
		pie->SetEntryLabel(point, label.c_str());
		
		point++;
	}
	
	pie->Draw("rsc");
}

A simple input file can be:

Blockquote
1 a
2 b
3 c

The above code produce an empty circle and only shows the first slice as if it were the only one (so it’s not a ‘slice’: it’s the entire pie).

What am I doing wrong?

2

yes the number of slices has to be know when creating the pie

void piechart2()
{
   Float_t vals[] = {.2,1.1,.6,.9,2.3};
   Int_t nvals = 5;
   TCanvas *cpie = new TCanvas("cpie","TPie test",700,700);

   TPie *pie2 = new TPie("pie2","",nvals);
   for (int i=0; i<nvals; i++) pie2->SetEntryVal(i, vals[i]);
   pie2->Draw("rsc");
}
1 Like
3

Isn’t there any method like “SetPoint” for TGraph? :frowning:

Actually I have a similar issue with TH1.

Well, ok… I’ll read the file twice in order to get the number of slices (which equals the number of lines).

Thanks!

4

No. (see TPie doc).
For TH1 it exists with alphanumeric labels.

5

We can imagine that SetEntryVal does that but it has to be implemented.

6

Blockquote
For TH1 it exists with alphanumeric labels.

o.O

I need to dig the TH1 reference page a bit deeper then.

Blockquote
For TH1 it exists with alphanumeric labels.

So it is a ‘planned feature’? Good.
Well, in the meanwhile, I’ll read the input file twice. :thinking:

Thank couet. :slight_smile:

7

No you are the first asking …
You are welcome to submit a PR if you need it fast,

1 Like
8

This is something I can’t do, not in a short time for sure, at least. And by ‘short time’ I mean: I’d need maybe even ~1 month to get confident with the TPie class.

I’d like to help, but well… :frowning:

9

Ok, so right now you should use your workaround.

1 Like
10

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