Conversion Specifiers in Root

[lasagna]

How do I properly use a conversion specifier in Root? Below is what I have right now, but I am getting an error message. What am I doing wrong?

for(int i=1; i<8257; i++){
    TH2I *h2 = (TH2I*)f->Get(Form("ch_ADC_max_all"));
    TH1D *h1 = h2->ProjectionY("ch%i_ADC" % i,i,i);

error: invalid operands to binary expression ('const char *' and 'int') TH1D *h1 = h2->ProjectionY("ch%i_ADC" % i,i,i);

Thank you!

[bellenot]

I don’t understand what you’re trying to do, but Form works this way:
Use something like:

TH2I *h2 = (TH2I*)f->Get("ch_ADC_max_all");
for (int i=1; i<8257; i++) {
   TH1D *h1 = h2->ProjectionY(Form("ch%d_ADC",i));

This will call:

   TH1D *h1 = h2->ProjectionY(Form("ch0_ADC");
   TH1D *h1 = h2->ProjectionY(Form("ch1_ADC");
   TH1D *h1 = h2->ProjectionY(Form("ch2_ADC");
   TH1D *h1 = h2->ProjectionY(Form("ch3_ADC");
...

And will complains because you replace (redefine) h1 at every loop iteration…

[lasagna]

I have a 2D histo with 8000 bins, and I need to make 8000 individual 1D histos from it (then analyze the histo, and move on to the next one).
I’m afraid I can’t write them all out explicitly because there are too many!

[bellenot]

Try:

TH1D *h1;
TH2I *h2 = (TH2I*)f->Get("ch_ADC_max_all");
for (int i=1; i<7999; i++) {
   h1 = h2->ProjectionY(Form("ch%d_ADC",i), i, i+1);

Cheers, Bertrand.

[bellenot]

use Form(), as in the previous example…

[lasagna]

It works! It all works! Thank you very much!!!

[bellenot]

You’re welcome