Re: Update histogram drawing in a loop

Hi James,

The essential part is to call c->Update() and/or gPad->Update(); The usual (fastest) pattern is as follow:

TCanvas *c = new TCanvas( ... );

[...]

if (i==0) {

    hist->Draw();
    c->Update();
} else if (i % 1000 == 0) {

    c->Modified();
    c->Update();
}

Cheers,
Philippe.

Christopher Jones wrote:
> Hi James,
>
> I've always done this by instantiating TCanvas myself, and then when
> you want to update the histogram, call TCanvas::Update().
>
> TCanvas *c = new TCanvas( ... );
>
> [...]
>
> if (i % 1000 == 0) {
> hist->Draw();
> c->Update();
> }
>
> Hope this helps.
>
> On Dec 10, 2008, at 4:29 PM, James Jackson wrote:
>
>> Hi,
>>
>> I would like to update the drawing of a histogram periodicially
>> within a loop where it is being filled, i.e.:
>>
>> TH2F *myHist = new TH2F("myHist", "Titles", 100, -5., 5., 100, 0.,
>> 20.);
>> etaGammaAcc->Draw("LEGO");
>>
>> for(Int_t i = 0; i < 5000000; ++i)
>> {
>> // Values for this iteration
>> Double_t val1 = someCalculation();
>> Double_t val2 = somOtherCalculation();
>>
>> // Fill the histogram
>> myHist->Fill(val1, val2);
>>
>> // Plot every 1000 iterations
>> if(i % 1000 == 0)
>> {
>> myHist->Draw("LEGO");
>> }
>> }
>>
>> However, this doesn't work - I only get a blank canvas displayed
>> until the loop exits (or I kill the script). Is there a way to do this?
>>
>> Regards,
>> James.
>>
>
>
>
>
>
>
Received on Thu Dec 11 2008 - 16:29:32 CET