Re: "files" on TFile

Rene Brun (Rene.Brun@cern.ch)
Mon, 06 Apr 1998 15:50:30 +0200


Mariusz Stanczak wrote:
>
> Hello,
> If someone, please, could help me understand a couple of things;
> first, after creating a directory on a .root file, how to actually put
> a "file" in that directory (in a .C macro)?
> Let me clarify... i have a time series data that lands itself nicely
> to the idea of a directory structure, as follows;
> root_file:/type/date/time <- this file would contain the data,
> which consists of a mixture of strings and floats.
> This seemed like the simplest way to pursue, but hours of reading
> the HTML docs still wouldn't point me to a way to write out, be it as a
> structure, or a class, the actual data.
>
> So, for the time being, I ended up with a combination of directories
> and TTree files, as follows;
> root_file:/type/date <- TTree containing the rest of data
> but with this scheme I've ran into a problem as well. I create the file
> OK, but getting the data back eluded me so far. I can loop through
> all the directories, all the trees and the branches in them, but things
> either blow up when I try to read the leaves containing the actual data,
> or I get incorrect values. I expected to get the data through TLeaf->
> GetValuePointer(), but it doesn't seem to be so. What am I missing here?
> This is all with a 2.03 version on NT.
>
> Thanks in advance,
>
> /Mariusz

I suggest you look at the URL:
http://root.cern.ch/root/HowtoWriteTree.html
This file describes the two techniques to write objects to a file.
For an example of Tree, look at the example provided
in $ROOTSYS/Test/Event.

I cannot give you more info without having more information
on what you want to do.

Rene Brun