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

[Jean-Louis Abitbol]

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
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