[R] Problem indexing a factor variable

[Ahmed, Rizwan]

Hi,

I have a dataframe "gexp_1" with 115 rows of samples and 27000 columns of gene expression measurements with each column corresponding to one gene. I now have a smaller vector of genes "tp" for which I need to pull out the data form the data frame.

#  first gene from the list with 16 genes

x <- tp[1,]
x
[1] geneA
16 Levels: geneA, geneB...

#unsuccessful
gexp_1$x
NULL

#or
gexp_1$x[1]
NULL

#but this works
gexp_1$geneA 

I am sure that this is a fundamental error on my part since I am new to R, I would appreciate any advice. I am trying to construct a for loop to analyze data for sets of genes at a time but stuck at this step.

Regards
Rizwan