Hi Georg,
The answer is in the warning message
In if (x < 0) a <- -1 else a <- 1 :
the condition has length > 1 and only the first element will be used
Basically you are passing a vector of length>1 to a control flow
expression (if() in this case) that requires only a vector of length
one. See ?Control or ?"if"
By the way, there is already an R function that returns the sign of a
numeric vector of any length. Its, of course, sign().
Julian
Georg Ehret wrote:
> Dear R,
> I am writing a simple function to extract the sign of values and apply it
> to a data frame (see below). Whatever I do I get error-messages... What is
> wrong?
>
> Thanking you in advance,
> Cheers, Georg.
> ***********************
> Georg Ehret
> Institute of Genetic Medicine
> Johns Hopkins University
> Baltimore
>
>
>> extractsign<-function(x){
> + if (x<0) a<--1
> + else a<-1
> + return (a)
> + }
>> a
> meanSBP meanSBP_tttcorr res_asb_SBP res_asb_SBP_tttcorr meanDBP
> meanDBP_tttcorr res_asb_DBP res_asb_DBP_tttcorr
> one -0.04 -0.01 -0.11 -0.05
> 0.18
> 0.24 0.18 0.24
> two 0.06 0.01 0.33 0.24
> 0.00
> -0.02 0.05 0.03
> three -0.01 0.01 -0.07 -0.01
> -0.01
> 0.00 -0.05 -0.01
> four -0.14 -0.05 -0.05 0.00
> -0.85
> -0.59 -0.79 -0.55
> five 0.12 0.06 0.17 0.07
> 0.34
> 0.21 0.60 0.44
> six -0.06 -0.01 -0.05 -0.01
> -0.26
> -0.14 -0.41 -0.25
>> lapply(a,extractsign)
> $meanSBP
> [1] -1
>
> $meanSBP_tttcorr
> [1] -1
>
> $res_asb_SBP
> [1] -1
>
> $res_asb_SBP_tttcorr
> [1] -1
>
> $meanDBP
> [1] 1
>
> $meanDBP_tttcorr
> [1] 1
>
> $res_asb_DBP
> [1] 1
>
> $res_asb_DBP_tttcorr
> [1] 1
>
> Warning messages:
> 1: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
> 2: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
> 3: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
> 4: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
> 5: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
> 6: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
> 7: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
> 8: In if (x < 0) a <- -1 else a <- 1 :
> the condition has length > 1 and only the first element will be used
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
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and provide commented, minimal, self-contained, reproducible code.
