transform() on selective names. Is it possible?
Wonderful, or the closest to heaven I've been the whole afternoon, but
not quite there:
# begin code
N <- 300
M <- 2
x <- matrix(data=rnorm(N*M, 0, 3)-10, ncol=M, nrow=N)
y <- matrix(c(1,-2,-2,1), ncol=M, nrow=M)
z <- data.frame(x %*% y)
colnames(z) <- c('x','y')
par(mfrow=c(1,3))
plot(z, pch=5, col="blue")
whiten <- scale # no need to re-invent the wheel, I agree
fc <- function(dfrm, coln) transform(dfrm, coln=whiten(dfrm[coln]))
colxy <- "x"
z1 <- fc(z, colxy) # the "[" function will interpret colxy
colnames(z1)
[1] "x" "y" "x.1"
fc <- function(dfrm, coln) transform(dfrm, coln=whiten(dfrm[,coln])) colxy <- "x" z2 <- fc(z, colxy) # the "[" function will interpret colxy colnames(z2)
[1] "x" "y" "coln"
#end code What I want is to know whether I can customize the column name of the result of the transform() call. Your hint is fantastic, thanks there, but I keep getting into that particular pattern of computation over and over and I wonder if it's possible to skip a column clean-up after applying your trick. 2011/4/7 David Winsemius <dwinsemius at comcast.net>:
On Apr 7, 2011, at 9:56 AM, Juan Carlos Borr?s wrote:
Hi all,
I am whitening my data:
# code begins
N <- 300
M <- 2
x <- matrix(data=rnorm(N*M, 0, 3)-10, ncol=M, nrow=N)
y <- matrix(c(1,-2,-2,1), ncol=M, nrow=M)
z <- data.frame(x %*% y)
colnames(z) <- c('x','y')
par(mfrow=c(1,3))
plot(z, pch=5, col="blue")
whiten <- function(x) { (x-mean(x))/sd(x) }
Consider: ?whiten <- scale ?# no need to re-invent the wheel ?fc <- function(dfrm, coln) transform(dfrm, coln=whiten(dfrm[coln])) ?colxy <- "x" ?z <- fc(z, colxy) ?# the "[" function will interpret colxy ?z
zz <- transform(z, x=whiten(x), y=whiten(y))
plot(zz, pch=3, col="red")
#code ends
And everything looks fine enough.
But now I want to withen just one of the columns and I won't know
which one until my script is running, hence I can't hard code it in
the script.
Then I though, well maybe if I define some convenient f...
#begin code
f <- function(a) { paste(a,"=withen(",a,")", sep='') }
a <- 'x' # or a <- 'y' depending on user input.....
f(a)
[1] "x=withen(x)"
# so I could try....
zzz <- transform(z, eval(f('x')))
# which of course doesn't work
plot(zz, pch=3, col="green")
head(z, n=2)
? ? ? ?x ? ? ? ? y 1 17.167380 ?6.884402 2 ?8.234507 13.940932
head(zzz, n=2)
? ? ? ?x ? ? ? ? y 1 17.167380 ?6.884402 2 ?8.234507 13.940932
#end code Could someone provide me with some hint on whether the attempted trick above is possible and how to proceed further? Thanks in advance. jcb!
______________________________________________ R-help at 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.
David Winsemius, MD West Hartford, CT
Cheers, jcb!