On Mar 30, 2010, at 9:24 PM, zubin wrote:
A general problem i run into, i know there must be a simple solution.
I like to create a variable by appending a 1 for example, (i need to
loop later on from 1 to X, thus the reason for this). So i assign
the
variable vplot with this value, however it has quotes and when i use
it
in a barplot, it throws an error. but the tcenter$X1 does exist,
its an
element of a data frame. So if i type directly it works, but i like
to
do this programmatically, as i have to generate a bunch of these plots
and need to loop.
So how do i concatenate to create a variable, then reference that
variable in a function call?
R> x <- data.frame(1,2,3,4,5,6,7,8)
R> x
X1 X2 X3 X4 X5 X6 X7 X8
1 1 2 3 4 5 6 7 8
R> x$X1
[1] 1
R> i=1
R> toplot <- paste("x$X",i,sep="")
R> toplot
[1] "x$X1"
Yes, except consider what happens when you offer "x$X1" to the
interpreter?
[1] "x$X1"
The interpreter does not take it any further because that character
object is atomic, at least I hope that is the correct terminology. You
would need to wrap it up in eval(parse(text= "x$X1") or
eval(parse(text=toplot)) to get it processed of as a language object.
okay lets test:
R> plot(x$X1)
-it works i see the plot
however this DOES not work
R> plot(toplot)
What about plot(x[1]) or plot(x[[1]]) or plot(x[i]) or plot(x[[i]])?
Those should all work.
Error in plot.window(...) : need finite 'ylim' values
In addition: Warning messages:
1: In xy.coords(x, y, xlabel, ylabel, log) : NAs introduced by
coercion
2: In min(x) : no non-missing arguments to min; returning Inf
3: In max(x) : no non-missing arguments to max; returning -Inf
Thus, that's my problem, i know it must be simple - the variable is
equal to x$X1 but it does not work in a function call? i tried many
functions - always some type of error.
I think we may need to see what you are planning on doing with this
knowledge, to know what sort of knowledge to offer.
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@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.
