[R] Character (1a, 1b) to numeric

[Bert Gunter]

... and continuing with this cute little thread...

I found the OP's specification a little imprecise -- are your values always
a string that begins with *some sort" of numeric value followed by "some
sort" of alpha code? That is, could the numeric value be several digits and
the alpha code several letters? Probably not, and the existing solutions
you have been provided are almost certainly all you need. But for fun,
assuming this more general specification, here is a general way to split
your alphanumeric codes up into numeric and alpha parts and then convert by
using a couple of sub() 's.

> set.seed(131)
> xc <- sample(c("1", "1a", "1b", "1c", "2", "2a", "2b", "2c"), 15, replace
= TRUE)
> nums <- sub("[[:alpha:]]+","",xc)  ## extract numeric part
> alph <- sub("\\d+","",xc)   ## extract alpha part
> codes <- letters[1:3] ## whatever alpha codes are used
> vals <- setNames(c(.3,.5,.7), codes) ## whatever numeric values to
convert codes to
> xnew <- as.numeric(nums) + ifelse(alph == "",0, vals[alph])
> data.frame (xc = xc, xnew = xnew)
   xc xnew
1  1a  1.3
2   2  2.0
3  1c  1.7
4  1c  1.7
5  1b  1.5
6  1a  1.3
7   2  2.0
8   2  2.0
9  1a  1.3
10 1a  1.3
11 2c  2.7
12 1b  1.5
13 1b  1.5
14  1  1.0
15 1c  1.7

Echoing others, no claim for optimality in any sense.

Cheers,
Bert


On Fri, Jul 10, 2020 at 12:28 PM David Carlson <dcarlson using tamu.edu> wrote:

> Here is a different approach:
>
> xc <-  c("1", "1a", "1b", "1c", "2", "2a", "2b", "2c")
> xn <- as.numeric(gsub("a", ".3", gsub("b", ".5", gsub("c", ".7", xc))))
> xn
> # [1] 1.0 1.3 1.5 1.7 2.0 2.3 2.5 2.7
>
> David L Carlson
> Professor Emeritus of Anthropology
> Texas A&M University
>
> On Fri, Jul 10, 2020 at 1:10 PM Fox, John <jfox using mcmaster.ca> wrote:
>
> > Dear Jean-Louis,
> >
> > There must be many ways to do this. Here's one simple way (with no claim
> > of optimality!):
> >
> > > xc <-  c("1", "1a", "1b", "1c", "2", "2a", "2b", "2c")
> > > xn <- c(1, 1.3, 1.5, 1.7, 2, 2.3, 2.5, 2.7)
> > >
> > > set.seed(123) # for reproducibility
> > > x <- sample(xc, 20, replace=TRUE) # "data"
> > >
> > > names(xn) <- xc
> > > z <- xn[x]
> > >
> > > data.frame(z, x)
> >      z  x
> > 1  2.5 2b
> > 2  2.5 2b
> > 3  1.5 1b
> > 4  2.3 2a
> > 5  1.5 1b
> > 6  1.3 1a
> > 7  1.3 1a
> > 8  2.3 2a
> > 9  1.5 1b
> > 10 2.0  2
> > 11 1.7 1c
> > 12 2.3 2a
> > 13 2.3 2a
> > 14 1.0  1
> > 15 1.3 1a
> > 16 1.5 1b
> > 17 2.7 2c
> > 18 2.0  2
> > 19 1.5 1b
> > 20 1.5 1b
> >
> > I hope this helps,
> >  John
> >
> >   -----------------------------
> >   John Fox, Professor Emeritus
> >   McMaster University
> >   Hamilton, Ontario, Canada
> >   Web: http::/socserv.mcmaster.ca/jfox
> >
> > > On Jul 10, 2020, at 1:50 PM, Jean-Louis Abitbol <abitbol using sent.com>
> > wrote:
> > >
> > > Dear All
> > >
> > > I have a character vector,  representing histology stages, such as for
> > example:
> > > xc <-  c("1", "1a", "1b", "1c", "2", "2a", "2b", "2c")
> > >
> > > and this goes on to 3, 3a etc in various order for each patient. I do
> > have of course a pre-established  classification available which does
> > change according to the histology criteria under assessment.
> > >
> > > I would want to convert xc, for plotting reasons, to a numeric vector
> > such as
> > >
> > > xn <- c(1, 1.3, 1.5, 1.7, 2, 2.3, 2.5, 2.7)
> > >
> > > Unfortunately I have no clue on how to do that.
> > >
> > > Thanks for any help and apologies if I am missing the obvious way to do
> > it.
> > >
> > > JL
> > > --
> > > Verif30042020
> > >
> > > ______________________________________________
> > > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > >
> >
> https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!V7p9rtNSgBWmF3KJ3U_01fR7vP_I7y-OnWHiTFxwRZ6bVJ3-emOwkBtcU3rSW6I$
> > > PLEASE do read the posting guide
> >
> https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!V7p9rtNSgBWmF3KJ3U_01fR7vP_I7y-OnWHiTFxwRZ6bVJ3-emOwkBtcg7nzsmk$
> > > and provide commented, minimal, self-contained, reproducible code.
> >
> > ______________________________________________
> > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >
> >
> https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!V7p9rtNSgBWmF3KJ3U_01fR7vP_I7y-OnWHiTFxwRZ6bVJ3-emOwkBtcU3rSW6I$
> > PLEASE do read the posting guide
> >
> https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!V7p9rtNSgBWmF3KJ3U_01fR7vP_I7y-OnWHiTFxwRZ6bVJ3-emOwkBtcg7nzsmk$
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]