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Christian Hoffmann

2001-Feb-22 11:11 UTC

[R] Setting elements in data frame

Hi all,

I have a problem which I am biting my teeth into unsuccessfully:

 (x <-
data.frame(S1=c("a","b","d","F"),N1=c(2,4,6,9),N2=c(6,NA,0,6)))
  S1 N1 N2
1  a  2  6
2  b  4 NA
3  d  6  0
4  F  9  6> is.na(x)     S1    N1    N2
1 FALSE FALSE FALSE
2 FALSE FALSE  TRUE
3 FALSE FALSE FALSE
4 FALSE FALSE FALSE

No I want to be able to do:
1) Setting all elements == 6 to 6000
x[x == 6] <- 6000
Error in [<-.data.frame(*tmp*, x == 6, value = 6000) : 
	matrix subscripts not allowed in replacement

But just would solve the problem.
So I tried to work with which():> (w <- which(x == 6,TRUE))  row col
3   3   2
1   1   3
4   4   3

But
x[w[,1],w[,2]] <- 6000;x
  S1   N1   N2
1  a 2     6000
2  b    4   NA
3  d 6000 6000
4  F 6000 6000

and not
x[w[,1],w[,2]] <- 6000;x
  S1   N1   N2
1  a 6000 6000
2  b      4   NA
3  d 6000      
4  F      9 6000


2) Setting all elements == NA to -1000
x[is.na(x)] <- -1000


What am I missing?

Thanks for help,

-christian
Dr.sc.math.Christian W. Hoffmann
Mathematics and Statistical Computing
Landscape Modeling and Web Applications
Swiss Federal Research Institute WSL 
Zuercherstrasse 111
CH-8903 Birmensdorf, Switzerland
phone: ++41-1-739 22 77    fax: ++41-1-739 22 15
e-mail: Hoffmann at WSL.CH
www: http://www.wsl.ch/staff/christian.hoffmann/

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Peter Dalgaard BSA

2001-Feb-22 13:17 UTC

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[R] Setting elements in data frame

Christian Hoffmann <christian.hoffmann at wsl.ch> writes:
> Hi all,
> 
> I have a problem which I am biting my teeth into unsuccessfully:
> 
>  (x <-
data.frame(S1=c("a","b","d","F"),N1=c(2,4,6,9),N2=c(6,NA,0,6)))
>   S1 N1 N2
> 1  a  2  6
> 2  b  4 NA
> 3  d  6  0
> 4  F  9  6
> > is.na(x)
>      S1    N1    N2
> 1 FALSE FALSE FALSE
> 2 FALSE FALSE  TRUE
> 3 FALSE FALSE FALSE
> 4 FALSE FALSE FALSE
> 
> No I want to be able to do:
> 1) Setting all elements == 6 to 6000
> x[x == 6] <- 6000
> Error in [<-.data.frame(*tmp*, x == 6, value = 6000) : 
> 	matrix subscripts not allowed in replacement
This seems to work, save for a (sort of spurious) warning that 6000 is
not a valid replacement value for the factor column:

x[,]<-lapply(x,function(z){z[z==6]<-6000;z})

(Why the comma? Search me...)
> 2) Setting all elements == NA to -1000
> x[is.na(x)] <- -1000
Same story..

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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Kaspar Pflugshaupt

2001-Feb-22 13:28 UTC

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[R] Setting elements in data frame

On Thursday 22 February 2001 12:11, Christian Hoffmann
wrote:> Hi all,
>
> I have a problem which I am biting my teeth into unsuccessfully:
>
>  (x <-
data.frame(S1=c("a","b","d","F"),N1=c(2,4,6,9),N2=c(6,NA,0,6)))
>   S1 N1 N2
> 1  a  2  6
> 2  b  4 NA
> 3  d  6  0
> 4  F  9  6
>
> > is.na(x)
>
>      S1    N1    N2
> 1 FALSE FALSE FALSE
> 2 FALSE FALSE  TRUE
> 3 FALSE FALSE FALSE
> 4 FALSE FALSE FALSE
>
> No I want to be able to do:
> 1) Setting all elements == 6 to 6000
Not elegant, nor fast, but works (old BASIC habits die hard):

 for (i in 1:nrow(x))
   for (j in 1:ncol(x))
     if (!is.na(x[i,j]) && x[i,j]==6)
        x[i,j] <- 6000

I'm sure there's a vectorized or otherwise much cleaner solution for
this...

> 2) Setting all elements == NA to -1000
> x[is.na(x)] <- -1000
can be done equivalently.
>
>
> What am I missing?
The problem seems to be that you cannot do a matrix subscript (which you 
would do with [is.na(x)] ) on a data frame. This probably is reasonable, 
since it would only work for simple (matrix-like) data frames. You might try 
to work on the data frame column-wise, since columns have the same data.class



Kaspar Pflugshaupt



-- 


Kaspar Pflugshaupt
Geobotanical Institute
ETH Zurich, Switzerland

http://www.geobot.umnw.ethz.ch
mailto:pflugshaupt at geobot.umnw.ethz.ch
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Kaspar Pflugshaupt

2001-Feb-22 13:34 UTC

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[R] Setting elements in data frame

On Thursday 22 February 2001 14:17, Peter Dalgaard BSA wrote:

> This seems to work, save for a (sort of spurious) warning that 6000 is
> not a valid replacement value for the factor column:
>
> x[,]<-lapply(x,function(z){z[z==6]<-6000;z})
>
> (Why the comma? Search me...)
>
Works also without the comma:

x <- data.frame(lapply(x,function(x) {x[x==6]<-6000;x}))

but still gives the warning.

Kaspar

-- 


Kaspar Pflugshaupt
Geobotanical Institute
ETH Zurich, Switzerland

http://www.geobot.umnw.ethz.ch
mailto:pflugshaupt at geobot.umnw.ethz.ch
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r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
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Jan Goebel

2001-Feb-22 13:46 UTC

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[R] Setting elements in data frame

Hello,

what about converting the data.frame to a matrix?

x <- data.matrix(x)
x[x==6] <- 6000
x <- as.data.frame(x)
x
  S1   N1   N2
1  2    2 6000
2  3    4   NA
3  4 6000    0
4  1    9 6000

best,

jan

On Thu, 22 Feb 2001, Christian Hoffmann wrote:
> Hi all,
> 
> I have a problem which I am biting my teeth into unsuccessfully:
> 
>  (x <-
data.frame(S1=c("a","b","d","F"),N1=c(2,4,6,9),N2=c(6,NA,0,6)))
>   S1 N1 N2
> 1  a  2  6
> 2  b  4 NA
> 3  d  6  0
> 4  F  9  6
> > is.na(x)
>      S1    N1    N2
> 1 FALSE FALSE FALSE
> 2 FALSE FALSE  TRUE
> 3 FALSE FALSE FALSE
> 4 FALSE FALSE FALSE
> 
> No I want to be able to do:
> 1) Setting all elements == 6 to 6000
> x[x == 6] <- 6000
> Error in [<-.data.frame(*tmp*, x == 6, value = 6000) : 
> 	matrix subscripts not allowed in replacement
-- 
+-----------------------------------
 Jan Goebel (mailto:jgoebel at diw.de)

 DIW Berlin 
 Longitudinal Data and Microanalysis
 K?nigin-Luise-Str. 5
 D-14195 Berlin -- Germany --
 phone: 49 30 89789-377
+-----------------------------------
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r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
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