MATLAB: How to number rows of a table by group

Question

I have a table with 2-3 rows per subject(PATID). Now, I would like to add a column which indicate if it is the first, second or third training of a patient (as shown in the figure). There must be a simple way, but I cant figure it out.

Thanks for your help

Answer 1

Can try something like this:

PATID = [1 1 3 3 3 5 9 9 12]'
T = table(PATID)
out = varfun(@(x)1:length(x),T,'InputVariables','PATID','GroupingVariables','PATID','OutputFormat','cell')
out = [out{:}]'

Just put out in a new column.