On Nov 19, 2009, at 4:39 AM, baptiste auguie wrote:
Hi,
Try this,
d <- data.frame(a=1:4, b=3:6)
var <- "a"
mean(d[var])
I tried get() on Simpson's pasted argument without success. Assuming
the OP still wanted to use only text arguments, then this approach works
dfn <- "d"
get(dfn)[var]
So get() works only on complete objects and not on expressions that
include extraction operations.
## or, if you are not aware of
## fortune("parse")
xx <- paste("d$",var, sep="")
mean(eval(parse(text=xx)))
HTH,
baptiste
2009/11/19 William Simpson <william.a.simp...@gmail.com>:
I have quite a complicated problem that's hard to describe.
Suppose I have a dataframe d. I want to access the vector d$var,
where
var is one of the variables in d. Just take for granted that
there's a
good reason I want to do this as follows.
var<-"DeOxyA"
xx<-paste("d$",var, sep="")
mean(xx)
[1] NA
Warning message:
In mean.default(xx) : argument is not numeric or logical: returning
NA
mean(d$DeOxyA)
[1] 21.98904
How can I convert xx so I can do mean(xx), for example? Currently xx
is a character, not a variable.
as.numeric doesn't do it. I want R to see
mean(DeOxyA), not
mean("DeOxyA")
I'm stumped.
Thanks very much for any help.
Bill
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______________________________________________
R-help@r-project.org mailing list
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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
Heritage Laboratories
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
