Re: Some Minor Difficulties with TH2D::Draw()

Rene Brun (Rene.Brun@cern.ch)
Fri, 20 Nov 1998 01:51:45 +0100

ryan roth wrote:
>
> Hello everyone:
>
> I have been developing a GUI application, similiar to the guitest
> program, which allows a user to pull information from an Objectivity
> database, fill a Histogram or Graph object, and then draw it to a canvas.
>
> As I was adding some 2D histogram functionality, I ran into some odd
> occurences I was hoping someone on this list could assist me with.
>
> First, I discovered that, if I use the DrawCopy() function of a TH2D, the
> plot style always defaults to a scatter plot, no matter what options I
> give it. Draw() works normally, but I would like to use DrawCopy(), as it
> would allow the user to rotate Lego and Surface plots.
>

Hy Ryan,
I cannot reproduce your problem. DrawCopy correctly saves
the drawing option into the copies histogram.

> Second, for some reason I cannot determine, whenever the 'SURF4' option
> is used, the surface always appears as pure white, with no shading
> whatsoever. To answer the obvious question, yes, I did change the color
> beforehand. I have been able to get the appropriate shading in a macro,
> but not in this application.

This, again, I cannot understand.

>
> Third, is it possible, in a standard 2D scatter plot, to increase the
> size of the points plotted? My application, at this time, typically
> involves a number of 'events' on the order of 50-100, rather than thousands.
> With the scatter plot points at their default size, the resultant plot is
> very hard to view.

You can use MarkerStyle 7 (bigger dots) or scalable marker 20.

>
> Other question I had regards 1D histograms -- is there some particular
> reason why they cannot seem to be drawn with a smooth curve or line AND
> markers? Whenever I try (in both macros and in my application) the
> resulting picture only includes markers.

Again, I do not understand. Did you try?
h->Draw("l"); // draw a line between points
h->Draw("c"); //draw a smooth line between points
h->Draw("p"); //draw marker at each point (use SetMarkerStyle)
h->Draw("cp"); draw a marker and a smooth line, etc

>
> It is possible that some of my difficulties arise from the fact that I am
> not running off of cint -- my application functions as a stand-alone
> program, which simply includes the ROOT libraries and starts using them
> (much like guitest does). It occured to me that opperating in this
> manner may leave some important variables or objects (which cint might
> automatically define) undeterminate, thus causing some of the library
> functions to operate improperly. Are there any objects, other than a
> TROOT and a TApplication, which should be declared in a program such as
> this? I should point out that my main() function is virtually identical
> to the one used in guitest.

No, this should be the same. We will need to see your application/code
for more investigation.

Rene Brun

>
> Thank you all for you assistance.
>
> Ryan Roth, New List Member
> PHENIX, BNL
> rothr@db.erau.edu