[R] Recode numbers

[William Dunlap]

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Lisa
> Sent: Wednesday, June 01, 2011 12:28 PM
> To: r-help at r-project.org
> Subject: Re: [R] Recode numbers
> 
> Thank you, Duncan,
> 
> Here "a" has the length of 24, and "b" has the length of 20 
> with numbers
> from 1 to 20 uniquely. I just want encode "a" from 1 to 20 
> based on "a"
> current order using "b". So, a1[1] = b[1] = 1
> a1[2] = b[2] = 5
> a1[3] = a1[4] = b[3] = 8 (since third and fourth numbers are 
> the same in
> "a")
> a1[5] = a1[6] = b[4] = 9
> a1[7] = b[5] = 14
> a1[8] = b[6] = 20
> a1[9] = b[7] = 3
> a1[10] = a1[11] = b[8] = 10
> ...
> a1[23] = b[19] = 15
> a1[24] = b[20] = 19

I don't understand the verbal description, but the the
following makes your example work:
  > b[cumsum(c(TRUE,a[-1]!=a[-length(a)]))]
   [1]  1  5  8  8  9  9 14 20  3 10 10 12  6 16  7 11 13 13
  [19] 17 18  2  4 15 19
  > identical(.Last.value, a1)
  [1] TRUE
Is that what you want?  The cumsum(...) increments each
at each changepoint in a.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 

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