[R] RODBC, missing values, and Excel

[Gabor Grothendieck]

I also got a strange result too (I renamed it sdr.read.xls
to distinguish it from read.xls in gdata and noticed that a
space got into my na's somehow so I used "na " for my
na.strings:

> sdr.read.xls("/test.xls", "Sheet2", na.strings = "na ")
     x
1 <NA>
2 <NA>
3   na
4   na
5   na
6   na
7 <NA>

I had more success using read.xls in the gdata package.
Note that we need to install perl first if not already present:

> library(gdata)  # for read.xls
> read.xls("/test.xls", 2, na.strings = "na ")
     x
1 0.11
2 0.11
3   NA
4   NA
5   NA
6   NA
7 0.11

> R.version.string # XP
[1] "Version 2.3.1 Patched (2006-06-04 r38279)"
> packageDescription("gdata")$Version
[1] "2.1.2"
> packageDescription("RODBC")$Version
[1] "1.1-7"


On 7/12/06, Sundar Dorai-Raj <sundar.dorai-raj at pdf.com> wrote:
> Hi, all,
>
> I'm trying to use RODBC to read data from Excel. However, I'm having
> trouble converting missing values to NA and rather perplexed by the
> output. Below illustrates my problem:
>
> ## DATA - copy to Excel and save as "tmp.xls"
> ## tmp.xls!Sheet1
> x
> 0.11
> 0.11
> na
> na
> na
> 0.11
>
> ## tmp.xls!Sheet2
> x
> 0.11
> 0.11
> na
> na
> na
> na
> 0.11
>
> ## R Code
> read.xls <- function(file, sheet = "Sheet1", ...) {
>   require(RODBC)
>   channel <- odbcConnectExcel(file)
>   sheet <- sprintf("select * from `%s$`", sheet)
>   x <- sqlQuery(channel, sheet, ...)
>   odbcClose(channel)
>   x
> }
>
> read.xls("./tmp.xls", "Sheet1", na.strings = "na")
> ## works as expected
> #     x
> #1 0.11
> #2 0.11
> #3   NA
> #4   NA
> #5   NA
> #6 0.11
>
> read.xls("./tmp.xls", "Sheet2", na.strings = "na")
> ## Huh? What happened?
> #   x
> #1 NA
> #2 NA
> #3 NA
> #4 NA
> #5 NA
> #6 NA
> #7 NA
>
>  > sessionInfo()
> Version 2.3.1 (2006-06-01)
> i386-pc-mingw32
>
> attached base packages:
> [1] "methods"   "stats"     "graphics"  "grDevices" "utils"     "datasets"
> [7] "base"
>
> other attached packages:
>   RODBC
> "1.1-7"
>
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