tutorial section: Parsing a subset of a GCTX file

[antonkratz]

In the tutorial, section "Parsing a subset of a GCTX file":
sig_ids <- col_meta$sig_id[idx]
This will not work because two lines earlier the metadata file has been loaded with row.names=1. So, there is no column sig_id anymore! Therefore sig_ids will be NULL (empty).

One solution would be to replace
sig_ids <- col_meta$sig_id[idx]
with
sig_ids <- row.names(col_meta[idx,]).

sig_ids is now a list of rownames.

[tnat1031]

thanks @antonkratz ! just pushed a fix