Writing a 2D array with pyroot

[etejedor]

Hello,

According to:

TTree 2D array

Hello, I am trying to save a 2D array data[2][20] in a TTree t. When I do everything is fine. But I would like to store arrays that can have variable size. So when I do t->Branch("n",&n,"n/I"); t->Branch("data",data,"data[2][n]/b"); I don’t get the data that I expect. I presume that a variable-size array is allowed, right? I appreciate some help to solve this problem. Examples of writing and reading the data are given below. Cheers, Roberval WriteData.C void WriteData() { unsigned …

t.Branch('mynum', n, 'mynum/I')
t.Branch('myarray', x, 'myarray[mynum][3]/D')

is not officially supported but “might work”. I guess you’ve tried already and there was no luck?

Another thing you could try is RVec:

https://root.cern/doc/master/classROOT_1_1VecOps_1_1RVec.html

If you look at the python docs in the link above, RVecs can adopt the memory of a numpy array. Once transformed into a (flat) RVec, you could then store it as with a vector branch. When retrieving it from the file, you would be able to retransform it into a numpy array with asarray but you’d also need to reshape it to get the original shape.