Read data from CSV file

[renqipan]

Hi experts,
I have data stored in a .csv file(name"ytt_yt.csv") as following picture. How can I read data from the csv file and plot a graph using the thrid and fourth columns? Take the third columns as x axis and the fourth column as y axis.
thank you
best regards,
Winston

[couet]

There is several posts on this topic in this forum. Have you tried to search the forum with “csv” ?

[renqipan]

I researched, but I didn’t get a clear answer.

[Wile_E_Coyote]

{
  TTree *t = new TTree("t", "tree from ytt_yt.csv");
  t->ReadFile("ytt_yt.csv", "yt0_X/D:yt0_Y:yt3_X:yt3_Y:yt1_X:yt1_Y:yt2_X:yt2_Y");
  t->Draw("yt3_Y : yt3_X");
}

[renqipan]

Hi Wile,
thank you. I tried your method, but it encountered an error:

Warning in TTree::ReadStream: Couldn’t read formatted data in “yt0_X” for branch yt0_Y on line 1; ignoring line
Warning in TTree::ReadStream: Read too few columns (2 < 8) in line 1; ignoring line
Warning in TTree::ReadStream: Ignoring trailing “,-0.0249839568,” while reading line 2
Warning in TTree::ReadStream: Ignoring trailing “,-0.0255424498,” while reading line 3
…

[Wile_E_Coyote]

Attach your “ytt_yt.csv” file for inspection.

[renqipan]

To upload the file I tranform the postfix into .txt, please first change it back to .csv.
Thanks for your attention.

ytt_yt.txt (17.3 KB)

[Wile_E_Coyote]

ROOT expects all lines with exactly 8 values separated by single “,” characters.
You need to remove “empty” / “nonexistent” values (i.e. there must be no “,,”).
Also, remove the very first line completely.