From: Steven McKinney <smckinney_at_bccrc.ca>

Date: Tue, 03 Jun 2008 19:19:49 -0700

[6,] 3 1 4

[7,] 1 9 -256

[6,] 3 1 4

[7,] 1 9 -256

R-help_at_r-project.org mailing list

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. Received on Wed 04 Jun 2008 - 02:23:43 GMT

Date: Tue, 03 Jun 2008 19:19:49 -0700

Hi Alan,

> -----Original Message-----

*> From: r-help-bounces_at_r-project.org on behalf of ALAN SMITH
**> Sent: Tue 6/3/2008 6:47 PM
**> To: r-help_at_r-project.org
**> Subject: [R] help understanding why #function(x,y) (if((x-y)>=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work likeI think it should
**>
**> Hello R users and developers,
**> I am trying to write several functions (fairly new at this) in order
**> to avoid using loops on large data frames (because they are slow). I
**> wrote the function below and it seems to get hung on the first part of
**> the if statement and then applies that condition to rest of the
**> function. So if (x-y) is greater than 0 the function uses the true
**> statement for the calculations. Could someone please offer some
**> advise on how to write these functions a little better or a type
**> "apply" that I may use with two (or more) different vectors of data
**> required by a single functions.
**> ####################### Examples
**> #######################################################
**> ## example 1 ###
**> x<-c(5,6,4,3,5,3,1)
**> y<-c(1,6,2,1,7,1,9)
**> folds<-function(x,y) (if((x-y)>=0) {2^(x-y)} else{-(2^abs(x-y))})
**> z<-folds(x,y)
**> check<-cbind(x,y,z)
**> View(check)
**>
**> Warning message:
**> In if ((x - y) >= 0) { :
**> the condition has length > 1 and only the first element will be used
**> ### why will it only use the first element and how to I get around
**> this ####
*

You probably want to use ifelse() instead of if()

folds <- function(x, y) (ifelse( ((x - y) >= 0), 2^(x - y), -(2^abs(x - y))))

x <- c(5,6,4,3,5,3,1)

y <- c(1,6,2,1,7,1,9)

folds <- function(x, y) (ifelse( ((x - y) >= 0), 2^(x - y), -(2^abs(x - y))))
z <- folds(x, y)

check <- cbind(x, y, z)

check

R> x <- c(5,6,4,3,5,3,1) R> y <- c(1,6,2,1,7,1,9) R> folds <- function(x, y) (ifelse( ((x - y) >= 0), 2^(x - y), -(2^abs(x - y)))) R> z <- folds(x, y) R> check <- cbind(x, y, z) R> check x y z [1,] 5 1 16 [2,] 6 6 1 [3,] 4 2 4 [4,] 3 1 4 [5,] 5 7 -4

[6,] 3 1 4

[7,] 1 9 -256

*>
*

> ## example 2 making the fist comparison negative ###

*> x1<-c(5,6,4,3,5,3,1)
**> y1<-c(11,6,2,1,7,1,9)
**> folds<-function(x,y) (if((x-y)>=0) {2^(x-y)} else{-(2^abs(x-y))})
**> z1<-folds(x1,y1)
**> check2<-cbind(x1,y1,z1)
**> View(check2)
**> Warning message:
**> In if ((x - y) >= 0) { :
**> the condition has length > 1 and only the first element will be
**> used
*

x1 <- c(5,6,4,3,5,3,1)

y1 <- c(11,6,2,1,7,1,9)

folds <- function(x, y) {ifelse( ((x - y) >= 0), {2^(x - y)}, {-(2^abs(x - y))} ) }
z1<-folds(x1,y1)

check2<-cbind(x1,y1,z1)

check2

R> x1 <- c(5,6,4,3,5,3,1) R> y1 <- c(11,6,2,1,7,1,9) R> folds <- function(x, y) {ifelse( ((x - y) >= 0), {2^(x - y)}, {-(2^abs(x - y))} ) } R> z1<-folds(x1,y1) R> check2<-cbind(x1,y1,z1) R> check2 x1 y1 z1 [1,] 5 11 -64 [2,] 6 6 1 [3,] 4 2 4 [4,] 3 1 4 [5,] 5 7 -4

[6,] 3 1 4

[7,] 1 9 -256

> ################################################################################

*> #### loop I am trying to avoid writing many many times #####
**> folds2<-NULL
**> xy<-as.data.frame(cbind(x,y))
**> for (i in 1:nrow(xy)) {
**> diff<-xy$x[i]-xy$y[i]
**> folds2[i]<-if(diff>=0) {2^diff} else{-(2^abs(diff))}
**> }
**> xyz<-cbind(xy,folds2)
**> View(xyz)
**> #################
**>
**> Thank you,
**> Alan
**>
**> P.S. why does ?function not work
*

It does work in my ESS R session buffer, so it depends on your setup.

try

R> ?"function"

?function

might not work as the R parser doesn't think you have finished typing in the expression (function objects are typically terminated by the final '}' brace).

*>
**> ______________________________________________
**> R-help_at_r-project.org mailing list
**> 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.
**>
**>
*

Best

Steve McKinney

R-help_at_r-project.org mailing list

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. Received on Wed 04 Jun 2008 - 02:23:43 GMT

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