[R] how to get all strings in a data frame that start with a particular string

[Ana Marija]

Thank you so much!

On Fri, Apr 10, 2020 at 12:00 PM Rasmus Liland <jensrasmus using gmail.com> wrote:
>
> On 2020-04-10 11:15 -0500, Ana Marija wrote:
> > I have a data frame (tot) with about
> > 2000 columns. How can I extract from
> > it all strings that start with E14?
> >
> > I tried this:
> > e14 <- sapply(tot, function(x) grepl("^E14", x))
> >
> > but this returns me just TRUE and
> > FALSE vector, how do I get actual
> > strings that start with E14?
>
> Dear Ana,
>
> perhaps you thought of something along
> the lines of this:
>
>   ncol <- 2000
>   nrow <- 3
>   line <-
>     c("a", "b",
>       "some text E14 bla bla some more text",
>       "d",
>       "E14 ... hey this starts and also ends with E14",
>       "E14 something-something",
>       "another string")
>   tot <-
>     as.data.frame(matrix(rep(line,
>       times=ncol*nrow),
>       ncol=ncol,
>       byrow=T))
>
>   # Now, tot is a df with some cells
>   # containing replicates of line, some
>   # cells there are now starting with E14
>   # ... so we need to convert it to a
>   # character matrix to be able to find
>   # the indecies of the cells starting
>   # with E14:
>
>   tot <- as.matrix(tot)
>   idx <- grepl("^E14", tot)
>   tot[idx]
>
> Best,
> Rasmus