multiple uses ifelse function

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multiple uses ifelse function

message
Readers,

Could someone please explain how to apply the function 'ifelse' to
change a vector, for various conditions?

testseq<-seq(1:20)
testchange<-ifelse(testseq<=4,'x',testseq)
testchange<-c(ifelse(testseq<=4,'x',testseq),ifelse(testseq>=5,'y',testseq))

The last instruction causes the vector 'testchange' to change
dimensions, when the result wanted is:

testchange
x x x x y y y y y y y y y y y y y y y y

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Re: multiple uses ifelse function

Jorge Cimentada
Hi Letter,

This should do it:
testchange <- ifelse(testseq <= 4,'x', ifelse(testseq >= 5, 'y', testseq))

Read it as: if testseq <=4, print x, ifelse test seq >=5, print y, any
other case, print testseq.

        [[alternative HTML version deleted]]

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Re: multiple uses ifelse function

PIKAL Petr
Hi

> -----Original Message-----
> From: R-help [mailto:[hidden email]] On Behalf Of Jorge
> Cimentada
> Sent: Tuesday, October 11, 2016 11:47 AM
> To: message <[hidden email]>
> Cc: [hidden email]
> Subject: Re: [R] multiple uses ifelse function
>
> Hi Letter,
>
> This should do it:
> testchange <- ifelse(testseq <= 4,'x', ifelse(testseq >= 5, 'y', testseq))

This is a little bit complicated.

Enough for this simple recoding is
testchange<-ifelse(testseq<=4,'x',"y")

However

testchange <- cut(testseq, breaks=c(0,4,21), labels=c("x","y"))

is more versatile as it can handle easily more than 2 levels.

Cheers
Petr

>
> Read it as: if testseq <=4, print x, ifelse test seq >=5, print y, any other case,
> print testseq.
>
>       [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> 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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Re: multiple uses ifelse function

S Ellison-2
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> -----Original Message-----
> testseq<-seq(1:20)
> testchange<-ifelse(testseq<=4,'x',testseq)
> testchange<-c(ifelse(testseq<=4,'x',testseq),ifelse(testseq>=5,'y',testseq))
>
> The last instruction causes the vector 'testchange' to change dimensions,

Of course it does. ifelse(test, yes, no) returns a vector of length length(test). Your last line concatenates two of them, so you'll get a vector of length 40.

You might also want to note that you are replacing numbers with character strings, so
ifelse(testseq<=4,'x',testseq)

will return four 'x's and then - because R has to coerce everything to a single type - character representations of numbers 5:20. That will not then respond well to subsequent numeric comparisons ...

S Ellison


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