Hi Alexander,
We have received a few similar requests in the past few months.
Using a TH2 object is convenient for points on a regular grid, but
not for your case.
Before leaving for holidays, Olivier Couet started the implementation
of a TGraph3D class. My guess is that this implementation will be available
in the middle of September.
Olivier, please inform Alexander and others who requested this feature
once it is in CVS.
Rene Brun
Alexander Wagner wrote:
>
> Hi!
>
> Seems my mail from yesterday didn't make it to the list.
>
> Just wondering wether this isn't possible an easier way.
> Consider a datafile of the following form:
>
> x1 y1 z1
> x1 y2 z2
> x1 y3 z3
>
> x2 y1 z4
> x2 y2 z5
> x2 y3 z6
>
> and so on. This is data for a 3D plot (a surface e.g.; for
> me this is 3D for root it seems to be 2D) and the format is
> "inspired by GNUplot". Now if I want to have a surface plot
> in GNUplot this is actually quite easy:
>
> splot "mydata.dta" using 1:2:3 with lines
>
> giving me a wireframe. Now GNUplot lacks, well, "some"
> functionality compared to root and I want to switch over to
> root. Unfortunately this simple kind of splot requires me
> quite a lot of code compared to the simple GNUplot approach,
> and till now I wasn't able to get something "easily
> reusable" like the line above. Would be something I'd really
> like to have. Some root function returning a TH2D or
> something where I can then use stuff like H2D->Draw("surf")
> or H2D->Draw("colZ").
>
> Did I miss something really simple?
>
> Seems to be that root already has everything needed, but
> always lacking a small part. E.g. I need to know the bining
> so a simple approach to just read in the datafile is not
> possible without having to calculate this one first. (Though
> root has functions to plot a T2F where it knows how to bin
> it.) Or I work arround this with quite a bit of code to
> count first the bins in each direction and then create a
> TH2D using the data counted and read in the file again.
> Stuff like that.
>
> It seems to get simpler if I create a root-file first and
> use that as input but simple is quite relative compared to
> the splot-command mentioned above ;)
>
> For TGraphs the solution is actually pretty simple as I can
> add points at the end of the TGraph. But I didn't find a way
> to add a new grid point to a TH2D. Seems that a TH2D needs
> to know how many points in each direction and which scale
> the axis has. So simply reading in the file doesn't work
> out. (Though it straight forward specifies each grid "line".)
>
> BTW: I know that root maybe doesn't really target this kind
> of data. In fact I use root mainly as a pretty good plotting
> program for my Fortran output. But well, it's really good!
> Except this nasty splot stuff. And even there root creates
> a lot better plots then the other tools I know of. It's just
> allways quite complex to do. (In the same direction: reading
> in Fortran of the form 1.23456789D-3 isn't that simple.
> Maybe it would be a good extension to handle the D as an e
> in a future release.)
>
> Thanks in advance for any hints.
>
> --
>
> Kind regards, / War is Peace.
> | Freedom is Slavery.
> Alexander Wagner | Ignorance is Strength.
> ----------------------------|
> Theoretische Physik II | Theory : G. Orwell, "1984"
> Universitaet Wuerzburg / In practice: USA, since 2001
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