[R] creating a variable using concatenation

[Peter Alspach]

Tena koe Zubin

Would this work for your application:

toPlot <- paste("X",i,sep="")
plot(x[, toPlot])

HTH ....

Peter Alspach

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of zubin
> Sent: Wednesday, 31 March 2010 2:25 p.m.
> To: r-help at r-project.org
> Subject: [R] creating a variable using concatenation
> 
> 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"
> 
> okay lets test:
> 
>  R> plot(x$X1)
> -it works i see the plot
> 
> however this DOES not work
> 
> R> plot(toplot)
> 
> Error in plot.window(...) : need finite 'ylim' values
> In addition: Warning messages:
> 1: In xy.coords(x, y, xlabel, ylabel, log) : NAs introduced by
coercion
> 2: In min(x) : no non-missing arguments to min; returning Inf
> 3: In max(x) : no non-missing arguments to max; returning -Inf
> 
> 
> Thus, that's my problem, i know it must be simple -  the variable is
> equal to x$X1 but it does not work in a function call?  i tried many
> functions - always some type of error.
> 
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