[Rd] extending the colClasses argument in read.table

2011-11-21 Thread Romain François 

Hello,

We've released the int64 package to CRAN a few days ago. The package 
provides S4 classes int64 and uint64 that represent signed and 
unsigned 64 bit integer vectors.


One further development of the package is to facilitate reading 64 bit 
integer data from csv, etc ... files.


I have this function that wraps a call to read.csv to:
- read the int64 and uint64 columns as character
- converts them afterwards to the appropriate type


read.csv.int64 - function (file, ...){
dots - list( file, ... )
if( colClasses %in% names(dots) ){
colClasses - dots[[colClasses]]
idx.int64 - colClasses == int64
idx.uint64 - colClasses == uint64

colClasses[ idx.int64 | idx.uint64 ] - character
dots[[colClasses ]] - colClasses

df - do.call( read.csv, dots )
if( any( idx.int64 ) ){
df[ idx.int64 ] - lapply( df[ idx.int64 ], as.int64 )
}
if( any( idx.uint64 ) ){
df[ idx.uint64 ] - lapply( df[ idx.uint64 ], as.uint64 )
}
df


} else {
read.csv( file, ... )
}
}

I was wondering if it would make sense to extend the colClasses argument 
so that other package can provide drivers, so that we could let the 
users just use read.csv, read.table, etc ...


Before I start digging into the internals of read.table, I wanted to 
have opinions about whether this would be a good idea, etc ...


Best Regards,

Romain

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http://romainfrancois.blog.free.fr

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Re: [Rd] extending the colClasses argument in read.table

2011-11-21 Thread Gabor Grothendieck 
2011/11/21 Romain François rom...@r-enthusiasts.com:
 Hello,

 We've released the int64 package to CRAN a few days ago. The package
 provides S4 classes int64 and uint64 that represent signed and unsigned
 64 bit integer vectors.

 One further development of the package is to facilitate reading 64 bit
 integer data from csv, etc ... files.

 I have this function that wraps a call to read.csv to:
 - read the int64 and uint64 columns as character
 - converts them afterwards to the appropriate type


Try this:

 library(int64)
 Lines - A\n12\n

 setAs(character, int64, function(from) as.int64(from))

 DF - read.csv(textConnection(Lines), colClasses = int64)

 str(DF)
'data.frame':   1 obs. of  1 variable:
 $ A:Formal class 'int64' [package int64] with 2 slots
  .. ..@ .Data:List of 1
  .. .. ..$ : int  0 12
  .. ..@ NAMES: NULL

To convince ourselves that its translating from character to int64:

 setAs(character, int64, function(from) {print(class(from)); 
 as.int64(from)})
 DF - read.csv(textConnection(Lines), colClasses = int64)
[1] character


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Re: [Rd] extending the colClasses argument in read.table

2011-11-21 Thread romain 
Thanks gabor, 

I will implement this and publish an updated package later. 

Cheers, 

Romain



Le 21 nov. 2011 à 16:31, Gabor Grothendieck ggrothendi...@gmail.com a écrit :

 2011/11/21 Romain François rom...@r-enthusiasts.com:
 Hello,
 
 We've released the int64 package to CRAN a few days ago. The package
 provides S4 classes int64 and uint64 that represent signed and unsigned
 64 bit integer vectors.
 
 One further development of the package is to facilitate reading 64 bit
 integer data from csv, etc ... files.
 
 I have this function that wraps a call to read.csv to:
 - read the int64 and uint64 columns as character
 - converts them afterwards to the appropriate type
 
 
 Try this:
 
 library(int64)
 Lines - A\n12\n
 
 setAs(character, int64, function(from) as.int64(from))
 
 DF - read.csv(textConnection(Lines), colClasses = int64)
 
 str(DF)
 'data.frame':   1 obs. of  1 variable:
 $ A:Formal class 'int64' [package int64] with 2 slots
  .. ..@ .Data:List of 1
  .. .. ..$ : int  0 12
  .. ..@ NAMES: NULL
 
 To convince ourselves that its translating from character to int64:
 
 setAs(character, int64, function(from) {print(class(from)); 
 as.int64(from)})
 DF - read.csv(textConnection(Lines), colClasses = int64)
 [1] character
 
 
 -- 
 Statistics  Software Consulting
 GKX Group, GKX Associates Inc.
 tel: 1-877-GKX-GROUP
 email: ggrothendieck at gmail.com

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