[R] paste / system mystery

[Uwe Ligges]

ivo_welch-rstat8303 at mailblocks.com wrote:

> Dear R wizards:
> 
> under R-2.1.0:
> 
> eargs <- 3:5;
> line <- paste(c("echo A B", eargs));
> cat("executing from R: '", line, "'\n");
> system(line);
> 
> Oddly, only "A" and "B" are echoed, not the eargs.  I had hoped that 
> line would be one string at this point, and for printing this seems to 
> be true.  However, unlist(line) still gives me the 4 components.  It 
> almost seems like the objects were not really pasted, but kept separate 
> [perhaps to conserve memory]---which works internally, but not 
> externally.
> 
> Is this my poor understanding of R, an R "feature," or an R bug?

Feature:
The arguments of paste() get pasted, and you have just specified one 
argument which is a character *vector*.
You want to say that the elements of the vector should be pasted as follows:

line <- paste(c("echo A B", eargs), collapse = " ")

Uwe Ligges




> help appreciated.
> 
> /iaw
> 
> 
> ---
> ivo welch
> 
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