subject:"\[R\] help understanding why #function\(x, y\) \(if\(\(x\-y\)=0\) \{2\^\(x\-y\)\} else\{\-\(2\^abs\(x\-y\)\)\}\)# doesn't work like I think it should"

[R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

2008-06-03 Thread ALAN SMITH

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 

## 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

 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

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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.

Re: [R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

2008-06-03 Thread Simon Blomberg

Use ifelse() rather than if () {} else {}. It's vectorized and very
useful for applying to elements along vectors. The latter idiom is much
better for control of flow in programs and functions.

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

 z - folds(x, y)
 z
[1]   16144   -44 -256
 

?function works for me. Here's my setup:

R version 2.7.0 (2008-04-22) 
x86_64-pc-linux-gnu 

Cheers,

Simon.


On Tue, 2008-06-03 at 20:47 -0500, ALAN SMITH wrote:
 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 
 
 ## 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
 
  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
 
 __
 R-help@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.
-- 
Simon Blomberg, BSc (Hons), PhD, MAppStat. 
Lecturer and Consultant Statistician 
Faculty of Biological and Chemical Sciences 
The University of Queensland 
St. Lucia Queensland 4072 
Australia
Room 320 Goddard Building (8)
T: +61 7 3365 2506
http://www.uq.edu.au/~uqsblomb
email: S.Blomberg1_at_uq.edu.au

Policies:
1.  I will NOT analyse your data for you.
2.  Your deadline is your problem.

The combination of some data and an aching desire for 
an answer does not ensure that a reasonable answer can 
be extracted from a given body of data. - John Tukey.

__
R-help@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.

Re: [R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

2008-06-03 Thread Erik Iverson


Alan -

ALAN SMITH wrote:

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 


When learning R, you have the power of the interpreter at all times. 
You have defined x and y above to be numeric vectors of length 7 each. 
Try typign x - y at the interpreter, and you'll see you get another 
numeric vector of length 7.  Now try (x - y) = 0 , and you'll get a 
logical vector of length 7.  However, if does not want a logical vector 
of length 7, it wants a logical vector of length 1, see the 'cond' 
argument of ?if.  However, the ifelse function should do what you want, 
see ?ifelse.


Here's an example using it

folds2 - function(x, y) {
  ifelse(x - y = 0, 2^(x - y), -(2^abs(x - y)))
}

folds2(x, y) should give you your answer...




## 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


Same idea as above here...




 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)
#


I'm not exactly sure what you'd like here, but hopefully with the above 
you can figure it out.  Let me know if you have any questions!


Best,
Erik Iverson



Thank you,
Alan

P.S.  why does ?function not work


What do you expect it to do?  It shows the help page for 'function' here.



__
R-help@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.


__
R-help@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.

Re: [R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

2008-06-03 Thread Gabor Grothendieck

Try this:

data.frame(x, y, folds = (x == y) + sign(x - y) * 2 ^ abs(x - y))

or replace data.frame with cbind if you prefer a matrix result.

On Tue, Jun 3, 2008 at 9:47 PM, ALAN SMITH [EMAIL PROTECTED] wrote:
 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 

 ## 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
 
  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

 __
 R-help@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.


__
R-help@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.

[R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

Re: [R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

Re: [R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

Re: [R] help understanding why #function(x, y) (if((x-y)=0) {2^(x-y)} else{-(2^abs(x-y))})# doesn't work like I think it should

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