Why do you want to do this via character strings at all?
You have at least two alternatives. First, you can pass the exponents as a
vector and the data as a matrix and then just do the calculation:
f <- function(mat, expon) {
apply(mat, 1, function(x, e) sum(x^e), e=expon)
#this relies on the vectorised nature of R and
particularly operators like ^
}
f(a, 1:3)
# [1] 1368 1779 2264 2829 3480
Alternatively, pass a function to your function:
f2 <- function(mat, fun, ...) {
apply(mat, 1, fun, ...)
}
f.to.pass <- function(x, e) sum(x^e)
f2(a, f.to.pass, e=1:3)
# [1] 1368 1779 2264 2829 3480
________________________________________
From: r-help-boun...@r-project.org [r-help-boun...@r-project.org] On Behalf Of
greatest.possible.newbie [daniel.h...@gmx.net]
Sent: 08 August 2012 22:16
To: r-help@r-project.org
Subject: Re: [R] Pass Conditional & loop argument into a function
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
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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