What does ^ symbol mean in an R regex?

Question

Does anyone what the ^ symbol means in R?

Here is the context:

mito.genes <- grep("^MT-", rownames(pbmc@data), value = T)

This command is used to extract only the mitochondrial genes from a large list of genes. This came from the Seurat tutorial which can be found here: https://raw.githubusercontent.com/satijalab/satijalab.github.io/master/seurat/pbmc-tutorial.Rmd

These mitochondrial genes all share the prefix "MT-" Example genes are MT-ND1, MT-ND2

I am trying to improve my understanding so i can adapt this command to extract other sets of genes by the characters in their names.

Thanks for your help

I have never used r in my life, but it could be some regex-pattern? There ^ means start of line — OptimusCrime, Feb 17 '17 at 16:10
It's not an R symbol really, but a regular expression symbol. — nrussell, Feb 17 '17 at 16:10
read this https://stat.ethz.ch/R-manual/R-devel/library/base/html/regex.html — Daniel, Feb 17 '17 at 16:13
I don't know R, but `grep` is a program used for searching through text. You can look at those docs: https://linux.die.net/man/1/grep — Christopher Schneider, Feb 17 '17 at 16:13
Outside of regular expressions, the `^` symbol denotes exponentiation, e.g., `2^3 = 8`. — Uwe, Feb 17 '17 at 16:14

score 0 · Accepted Answer · answered Feb 17 '17 at 16:12

0

It is a regex meaning it start with MT. so basically whenever you have "^MT-" it means looking for anything which start with MT-

answered Feb 17 '17 at 16:12

Daniel

1 Answers1