[R] Changingvalues in data frame

[Peter Wolf]

Frank Gerrit Zoellner wrote:

>Hi!
>
>I have a question concerning data frames and changing particular values in it.
>
>I have set up a data frame containing n rows of observations od dimension m, so in each row there is a vector of size m. Now I want to introduce a cut off to tha data. Therfore I caluclated the mean and variance within each column using apply:
>
>me<-apply(daten[1:72],2,mean)
>st<-apply(daten[1:72],2,var)	
>
>Now I want use the mean and the var to form a cut off value, and apply it to each row of the data frame.
>
>I tried the following
>
>cutoff<-function(x){
>      if(x>me+2*st){
>        x<-me+2*st
>      }
>    }
>
>cutd<-apply(daten[1:72],1,cutoff)
>
>but I have to supply somehow the column index to me and st.
>Any Ideas ?
>Thanks,
>Frank
>  
>
what about:

x<-as.data.frame(matrix(rnorm(100),20,5))
apply(x,2,function(x){limit<-mean(x)+1*sqrt(var(x)); 
ifelse(x>limit,1000*limit,x)})

or

apply(x,2,function(x){limit<-mean(x)+2*sqrt(var(x)); 
ifelse(x>limit,limit,x)})



Peter