[R] Extracting numbers from a character variable of different types

[David Winsemius]

On Mar 18, 2012, at 10:44 AM, irene wrote:

> Hello,
>
> I have a file which contains a column with age, which is represented  
> in the
> two following patterns
>
> 1. "007/A" or ''007/a" or ''7 /a" ..... In this case A or a means  
> year and I
> would like to extract only the numeric values eg 7 in the above case  
> if this
> pattern exits in a line of file.
>
> 2. "004/M" or "004/m" where M or m means month ...... for these  
> lines I
> would like to first extract the numeric value of Month eg. 4  and then
> convert it into a value of years, which would be 0.33 eg 4 divided  
> by 12.

I thought it easier to get to months as an initial step:

 > dfrm <- read.table(text="'007/A'\n'007/a' \n '7 /a '\n '004/ 
M'\n'004/m'")

 > dfrm$agenew <- sub("(^\\d+\\s*)(/)([aA])","\\1 * 12", dfrm$V1)
 > dfrm$agenew2 <- sub("(^\\d+\\s*)(/)([mM])","\\1", dfrm$agenew)
 > dfrm$agenew2
[1] "007 * 12" "007 * 12" "7  * 12 " "004"      "004"
 > eval(parse(text=dfrm$agenew2))
[1] 4
 > sapply(dfrm$agenew2, function(x) eval(parse(text=x)) )
007 * 12 007 * 12 7  * 12       004      004
       84       84       84        4        4


>
> Can anyone help?
>
> Thank you
>
> --
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David Winsemius, MD
West Hartford, CT