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

2008-02-26 Thread Michael Anyadike-Danes 
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  117.19NaN 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   NaNNA  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   NaNNA  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   NaNNA  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   NaNNA  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\)

 





Economic Research Institute of Northern Ireland

Floral Buildings

2-14 East Bridge Street

Belfast BT1 3NQ

Tel:  (028) 90727362

Fax: (028) 90319003




[[alternative HTML version deleted]]

__
R-help@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.

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

2008-02-26 Thread Bert Gunter 
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

__
R-help@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.

__
R-help@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.