Retrieve data from column plus x

I have a large set of data that contains information about numerous different core samples. Each core sample has a different amount of sections, the amount of sections for each specific core is stipulated in column 13. I need to find out the length of each core sample, this information is provided in the final section length. So if the value in column 13 was 6, the length of the core would be found in column 19. As each core has different amount of sections how would I extract information regarding the length of each individual core?

Answer 1

[Walter Roberson]

final_len_col = 13 + coredata(:,13);
final_len_idx = sub2idx(size(coredata), 1:size(coredata,1), final_len_col);
final_lengths = coredata(final_len_idx);

This can be abbreviated

final_lengths = coredata((1:size(coredata,1)).' + size(coredata,1) * ((13-1) + coredata(:,13)));

[Natalie]

Thank you!! Worked perfectly.