[R] R 3.1 changes to type.convert causing strings where I used to get numeric

[Bos, Roger]

Duncan,

Yes, I admit I haven't updated since 2.15.2 so I was behind.  I am seeing the same problem with reading from RODBC (sql server) tables.  I write data to a table and then read it back.  In R 2.15 it would come in numeric.  Under R 3.1 it comes in as a string.

Thanks,

Roger


-----Original Message-----
From: Duncan Murdoch [mailto:murdoch.duncan at gmail.com]
Sent: Wednesday, April 30, 2014 4:40 PM
To: Bos, Roger; r-help at r-project.org
Subject: Re: [R] R 3.1 changes to type.convert causing strings where I used to get numeric

On 30/04/2014, 4:20 PM, Bos, Roger wrote:
> Dear R-help,
>
> I recently upgraded to R 3.1 patched and code that ran fine previously and now giving a lot of errors because the data is coming in as strings instead of numeric.  I can fix my code to wrapping each item I want to use with as.numeric(), but that seems very inefficient.
>
> I looked at the change list for R 3.1 and I see the first item is a change in type.convert() that seems to be causing me grief.  The suggestion is to use colClasses, but when I try to do so I get an error regarding the quotes again...
>
>>        ann1  <- read.table(driveletter %+% "/snap/ann/snap_fyr_ann1_"
>> %+% i %+% ".txt", header=TRUE, quote="", as.is=TRUE,
>> colClasses='numeric')
> Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings,  :
>    scan() expected 'a real', got '"1033.7"'
>
> Does anyone have any suggestions?

This sounds like two separate problems.  The first is the change to type.convert().  That's going to be dealt with (it's already in R-devel, will eventually be handled in R-patched and 3.1.1).  You deserve part of the blame for this for never testing the pre-release version.  It would have been easier to fix before release, but nobody who tested then bothered to report it.

The second problem is one I don't recall hearing reported before.  If you have a .csv file containing the lines

X
"1"

then it should be readable as a .csv, because the quotes should be stripped.  In fact it is readable now if you *don't* specify that the column is numeric, and it will be converted to a numeric value.
However, if you do use colClasses="numeric" you'll get an error.  That looks wrong, though it is consistent with ?read.table.

 > x <- c("X", '"1"')
 > read.csv(textConnection(x))
   X
1 1
 > read.csv(textConnection(x), colClasses="numeric") Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings,  :
   scan() expected 'a real', got '"1"'
 >


Duncan Murdoch

>
>
> CHANGES IN R 3.1.0:
> NEW FEATURES
>
>
> type.convert() (and hence by default read.table()) returns a character vector or factor when representing a numeric input as a double would lose accuracy. Similarly for complex inputs.
> If a file contains numeric data with unrepresentable numbers of decimal places that are intended to be read as numeric, specify colClasses in read.table() to be"numeric".
>
>
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