As Thomas Lumley has frequently noted, eval(parse...)) should generally be
avoided.
You probably want do.call(), as in
## warning: UNTESTED
lapply(numbs,
function(n)do.call(read.xls,list(file=paste("Book",n,".xls",sep=""),sheet=1,
...))) ## ... contains the other explicitly names arguments
Note that this would automatically create your list for you.
Cheers,
Bert Gunter
Genentech Nonclinical Statistics
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Erik Iverson
Sent: Tuesday, February 26, 2008 9:29 AM
To: Michael Anyadike-Danes
Cc: r-help@r-project.org
Subject: Re: [R] using eval-parse-paste in a loop
> ############### stripping off eval, looking for clues
>
>
>
> parse(paste('read.xls("Book',nam,'.xls",sheet=1,from=4,colClasses="numer
> ic")',sep=''))
>
> Error in file(file, "r") : unable to open connection
>
> In addition: Warning message:
>
> In file(file, "r") :
>
> cannot open file
> 'read.xls("Book1.xls",sheet=1,from=4,colClasses="numeric")', reason
> 'Invalid argument'
>
Your clue is that it looks like parseis unsuccessfully trying to open a
file. Look at ?parse and note the first argument, which you are using
because of positional matching.
You want eval(parse(text = paste(...)))
Best,
Erik Iverson
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