For one of my analysis I need to calculate TPM values. Unfortunately, I have only a count matrix with row HUGO annotated genes and columns are the samples. Unfortunately, our collaborator have deleted all intermediate steps so I have only the counts and a gtf table that is used to calculate the counts. For calculation of TPM I need gene lengths which I can get from the gtf file. However, I am not sure how accurate this would be not knowing which exons are expressed. Any one has any experience on this? Do I need to do the analysis from scratch (redo all star + feature counts for all my 200 samples)?