[R] help with vector operation

[Uwe Ligges]

eesteves at ualg.pt wrote:

> Dear All,
> 
> I'm trying to calculate the following:

Select the rows of the data.frame and just calculate what you already 
have written:


> g.rate<-(SL-int)/NO

For the lines you cited this means, e.g.:

   X <- data.frame(CODE = c(123:125, 234),
                   SL = c(12.5, 11.4, 10.8, 16.9),
                   NO = c(14, 13, 11, 19),
                   DAY = c(88, 88, 101, 172))
   int <- c(9.32, 8.43, NA, 9.81)
   g.rate <- with(X, (SL - int) / NO)


That's it!

Uwe Ligges



> where SL and NO are individual length and counts for the same subject, and the
> int value is a day-specific value i.e. for each DAY=88, 101..., 172 I'd like to
> use a different values of int=9.32, 8.43, ..., 9.81. All variables are compiled
> in a larger data.frame of the form:
> 
> CODE  SL    NO  DAY (...)
> 123   12.5  14  88
> 124   11.4  13  88
> 125   10.8  11  101
> (...)
> 234   16.9  19  172 (...)
> 
> I've been trying apply() but with little (NONE) success!
> Thanks, Eduardo Esteves
> 
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