On Aug 8, 2012, at 2:16 PM, greatest.possible.newbie wrote:
Ok I see that point with the quotes. But what I want to do still
doesn't
work:
a <- matrix(1:15,ncol=3)
b <- paste( paste("a[," ,paste(1:3), "]",sep="")
,"^",1:3,sep="",collapse="+")
b
#[1] "a[,1]^1+a[,2]^2+a[,3]^3"
#instead of (which I want)
a[,1]^1+a[,2]^2+a[,3]^3
#[1] 1368 1779 2264 2829 3480
You want to evaluate that object which is not yet an expression. The
parse function will turn it into an expression and then eval will work:
> eval( parse(text=b) )
[1] 1368 1779 2264 2829 3480
Here's another approach:
> colnames(a) <- c("alin", "asqr", "acube")
> adat <- as.data.frame(a)
> with( adat, alin+asqr^2+acube^3)
[1] 1368 1779 2264 2829 3480
--
David
or I want to change some function input (dramatically) just by
changing two
conditional arguments (in my case constant and c).
a <- matrix(1:15,ncol=3)
b <- matrix(NA,nrow=nrow(a),ncol=ncol(a))
constant <- 1
c <- 5
for (j in 1:ncol(a))
b[,j] <- mapply(function(x){
if(is.null(constant)) {paste(paste("x^", paste(1:c) , sep="",
collapse="
+ ") , ", a[,",j,"]" ,sep=" ")
} else if(!is.null(constant)) {paste(paste(constant, paste("x^",
paste(1:c) , sep="",collapse="+"),collapse="+") , ",
a[,",j,"]" ,sep=" ") }
})
By the way.. Can anyone tell my why collapse doesn't work in outer
paste
function?
--
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Sent from the R help mailing list archive at Nabble.com.
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
