Re: [R] using eval-parse-paste in a loop

From: Tony Plate <tplate_at_blackmesacapital.com>
Date: Tue, 26 Feb 2008 10:57:21 -0700

Using eval-parse for this looks like overkill. You should just be able to do something straightforward like:

for (i in 1:120)

   assign(paste("book", i, sep=""), read.xls(paste("Book", i, ".xls", sep=""), sheet=1, from=4, colClasses="numeric"))

which would put your spreadsheets in variables book1, book2, etc.

Or, if you want to put everything in a list:

books <- lapply(1:120, function(i) read.xls(paste("Book", i, ".xls", sep=""), sheet=1, from=4, colClasses="numeric"))

BTW, the reason your attempts with parse() were failing is that default argument of parse() is a filename (do args(parse) to see this quickly). You wanted parse(text=...).

Michael Anyadike-Danes wrote:
> R-helpers
>
>
>
> I have 120 small Excel sheets to read and I am using
> library(xlsReadWrite): one example below.
>
>
>
> I had hoped to read sheets by looping over a list of numbers in their
> name (eg Book1.xls, Book2.xls, etc).
>
>
>
> I thought I had seen examples which used eval-parse-paste in this way.
>
>
>
> However, I have not been able to get it to work..
>
>
>
> 1. is this a feasible approach?
>
>
>
> 2. if not advice would be welcome.
>
>
>
> 3. Equally, advice about a better approach would also be v. welcome.
>
>
>
> I haven't included the data because my failed attempt is
> data-independent (and probably more basic).
>
>
>
>
>
> Michael Anyadike-Danes
>
>
>
> ############# show that read.xls works
>
>
>

>> test <- read.xls("Book1.xls",sheet=1,from=4,colClasses="numeric")

>
>> str(test)

>
> 'data.frame': 23 obs. of 13 variables:
>
> $ Off.Flows..Thousands.: num 117.19 NaN NA 1.43 2.26 ...
>
> $ Off.Flows..Thousands.: num 8.42 NaN NA 0.08 0.11 0.01 0.11 1.59 0.16
> 0.04 ...
>
> $ Off.Flows..Thousands.: num 20 NaN NA 0.2 0.3 0.02 0.32 4.39 0.41
> 0.11 ...
>
> $ Off.Flows..Thousands.: num 12.36 NaN NA 0.14 0.27 ...
>
> $ Off.Flows..Thousands.: num 7.59 NaN NA 0.11 0.18 0.01 0.14 1.46 0.23
> 0.06 ...
>
> $ Off.Flows..Thousands.: num 10.31 NaN NA 0.12 0.23 ...
>
> $ Off.Flows..Thousands.: num 7.55 NaN NA 0.08 0.2 0.01 0.11 1.6 0.23
> 0.05 ...
>
> $ Off.Flows..Thousands.: num 10.57 NaN NA 0.19 0.21 ...
>
> $ Off.Flows..Thousands.: num 9.36 NaN NA 0.13 0.26 0.02 0.13 2.12 0.27
> 0.07 ...
>
> $ Off.Flows..Thousands.: num 8.21 NaN NA 0.1 0.19 0.01 0.1 1.9 0.23
> 0.06 ...
>
> $ Off.Flows..Thousands.: num 9.04 NaN NA 0.13 0.11 0.01 0.17 1.54 0.17
> 0.05 ...
>
> $ Off.Flows..Thousands.: num 13.42 NaN NA 0.14 0.19 ...
>
> $ Off.Flows..Thousands.: num 0.37 NaN NA NaN 0.01 NaN 0.01 0.05 0.02
> NaN ...
>
>
>
> ############### simple minded attempt substituting eval-parse-paste
>
>
>
>> nam <- 1

>
>
>
>> test <-

> eval(parse(paste('read.xls("Book',nam,'.xls",sheet=1,from=4,colClasses="
> numeric")',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'
>
>
>
> ############### 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'
>
>
>
> ############### stripping off parse, still looking for clues
>
>
>
> paste('read.xls("Book',nam,'.xls",sheet=1,from=4,colClasses="numeric")',
> sep='')
>
> [1] "read.xls(\"Book1.xls\",sheet=1,from=4,colClasses=\"numeric\")"
>
>
>
> ################################
>
>
>
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R-help_at_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. Received on Tue 26 Feb 2008 - 17:59:43 GMT

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