[R] creating a variable using concatenation

[Steve Chen]

You can try this:

library(tutoR)
plot(eval.string(toplot))


Steve Chen

On 2010/3/31 上午 09:24, 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"
> 
> 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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