How to the decrease the number of Label of Draw(time:x)

ROOT
1

Hello,
I want to read in Data of a Tree file, as usual with date and time columns. Like that:
2010-04-29 15:20:49.335 0 1 2 3
2010-04-29 15:21:09.735 0 0 0 0
2010-04-29 15:21:30.135 0 0 2 0
2010-04-29 15:21:50.535 0 0 0 0
2010-04-29 15:22:10.935 0 0 0 0

I read in the Time/Data as Ch. like that:
tree->ReadFile(“name.txt”,“year/C:time:l1/D:l2:l3:l4”);

Now I want to Draw something like:
Draw(“time:l1>>h1”);

As I have a lot of 10.000 lines and even more there are always too much Labels drawn…
I tried allready to change h1 with:
SetNdivision or
as a Time axis

And some other things, which I already found in the forum or the user guide. Nothing worked.
At least I would have to decrease the number of labels or even better to include the days at the same axis. As this format of variables is quite usual, I maybe thought to be not the only one thinking about that…
Thanks Wolfgang

2

If you read the dates as character strings, you will have one bin per date each of them labelled with a character string (a date). That’s the definition of an histogram with alpha numeric labels. There is no way to reduce the number of labels for such histograms: by definition all the bins must be visible. What you want is a time axis. In that case you should convert the date into integers with TDatime and stored these numbers in your tree instead of the character string.
More details here: root.cern.ch/drupal/content/how- … time-units

3

Thank you,
I still have problems, I tried to convert the date with:
TDatime T0(2010,04,29,15,20,49.335);
int XO = T0.Convert();

So I’m not sure, if everything is alright with the seconds (they are no integers) and I didn’t find the command how to take exactly the data from one tree, to convert them and over all how to store them afterward in the same tree. I hope its not just a simply thing, but somehow I can’t see it…

4

As you can see here : root.cern.ch/root/html/TDatime.html
TDatime takes 6 integers.

5

Yes, that’s the problem. Furthermore I can’t find anything about taking the data from the tree convert them and put them back…maybe I have to search somewhere else for that??

6

Instead of using TTree::ReadFile, read line by line and convert your date/time into more appropriate units.
see example in $ROOTSYS/tutorials/tree/cernbuild.C

Rene

7

I’m sorry but I didn’t manage it. I can’t see how to convert the time data to reach right time axis. If I separate seconds, minutes,… I won’t be able to draw something without containing a lot of data at the next time dimension (hours…). I thought, as many people are working with “timber” that there is a more convenient solution.