Removing Rows From a Matrix by Label Quickly
2 views (last 30 days)
Show older comments
I currently have some code that is destined to: import data as a matrix from a text file, read the data and delete any rows in the matrix that do not start with "H", delete the H label from the remaining rows, print this matrix to a text file. My code is as follows:
FID = fopen('Test_Data_2.txt','rt');
m = [m;str2num(l(2:end))];
FID = fclose(FID);
dlmwrite('md_msd.out', m, 'delimiter', '\t', ...
This code works great for small data sets but I am going to have to use it for sets of 100000 rows or more. I need a way to speed up the process as my current code takes far too long. Is there any way I can make this code faster?
Walter Roberson on 26 Jun 2013
Use other tools when it makes sense to do so. For example, in Linux or OS-X from their shells:
sed -e '/^$|^[^H]/d', -e 's/^H//p' < Test_Data_2.txt > md_msd.out
perl -e '/^H/ && s/^H// && print' < Test_Data_2.txt > md_msd.out
You can invoke perl from within MATLAB using the perl() command.
Find more on Text Files in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!Start Hunting!