Re: [ROOT] Arrows on histograms

From: Rene Brun (Rene.Brun@cern.ch)
Date: Mon Jun 02 2003 - 21:40:53 MEST


Hi Kevin,

If you are brave to make an implementation, I have the following
suggestions.
 - Create a TGraphArrows class derived from TGraph for the 2-D case.
   See TGraphErrors for an example. TGraph has already all the
   infrastructure for drawing, computing the range and also supports
   picking.

 - We do not have a TGraph3D class. It would be nice to have one.
   In this case, TGraph3DArraows would make sense.

 - Do not restrict the implementation to the case of histograms.On 

my 2 cents

Rene Brun

Thu, 29 
May 2003, Kevin Reil wrote:

> Hi Rene,
> 
> Thanks, I knew I could draw the arrows using TArrow. What I have is a 6
> dimensional array, 3 coordinates are position, 3 coordinates are a
> direction for that position (photon location and direction).  I make a cut
> on which photons make it through an aperture and want to plot the location
> and direction of these photons. I was hoping there was a prebuilt way to
> do this.
> 
> So first I plot the random mess of arrows and positions at the photon
> source. Then plot the same plot of photons which make it through the hole
> and see that all the arrows are pointing towards one location
> 
> Something like:
> TH2Arrows(Float_t pos[2], Float_t dir[2]);
> TH3Arrows(Float_t pos[3], Float_t dir[3]);
> 
> I did not expect these to be prebuilt but perhaps someone had an example
> readily available. I am sure I can come up with one if no one has one (so
> please don't take your time to do it if it's not ready).
> 
> Cheers,
> Kevin
> 
> 
> 
> |------------------------------------|---------------------------------|
> | Kevin Reil                         | 2575 Sand Hill Road, MS 26      |
> | X2447, 103D A&E Bldg. 041          | Menlo Park, CA 94025            |
> |------------------------------------|---------------------------------|
> | http://www.slac.stanford.edu/~reil | Office (650) 926-2447           |
> | reil@slac.stanford.edu             | Home   (650) 938-1767           |
> | http://reil.no-ip.org              | Fax    (650) 926-5368           |
> |----------------------------------------------------------------------|
> |                    And my father dwelt in a tent.                    |
> |----------------------------------------------------------------------|
> 
> On Thu, 29 May 2003, Rene Brun wrote:
> 
> >Hi Kevin,
> >
> >What is the problem? You can create a TArrow object for each
> >of your points (new TArrow(xmin,ymin,xmax,ymax))
> >where xmin,ymin, etc are computed from the bin coordinates.
> >It may be more convenient to create one single TArrow, set
> >its graphics attributes (line width, angle, etc),
> >and use TArrow::DrawArrow to make a new instance.
> >
> >Note that you can also add the TArrow objects
> >to hist->GetListOfFunctions(). When drawing the histogram,
> >the arrows will be automatically drawn.
> >
> >
> >Rene Brun
> >
> >On Wed, 28 May
> >2003, Kevin Reil wrote:
> >
> >> Hi,
> >>
> >> I would like to ba able to draw an arrow on each point plotted in 2d and
> >> 3d histograms.
> >>
> >> IE at point (2,3) draw a unit arrow pointing in direction (1,0)
> >> and loop over points...
> >>
> >> Or
> >> at point (1,1,1) a unit arrow pointing in direction (0,1,1)
> >> and loop of points...
> >>
> >> etc
> >>
> >> Is there a quick way?
> >>
> >> Cheers,
> >> Kevin
> >>
> >> |------------------------------------|---------------------------------|
> >> | Kevin Reil                         | 2575 Sand Hill Road, MS 26      |
> >> | X2447, 103D A&E Bldg. 041          | Menlo Park, CA 94025            |
> >> |------------------------------------|---------------------------------|
> >> | http://www.slac.stanford.edu/~reil | Office (650) 926-2447           |
> >> | reil@slac.stanford.edu             | Home   (650) 938-1767           |
> >> | http://reil.no-ip.org              | Fax    (650) 926-5368           |
> >> |----------------------------------------------------------------------|
> >> |                    And my father dwelt in a tent.                    |
> >> |----------------------------------------------------------------------|
> >>
> >
> >
> 



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