[R] Updating a worksheet in Excel file using RODBC

[Prof Brian Ripley]

Yes, sqlDrop does not work correctly for Excel worksheet names (and there 
are other quirks).

As I said in another message, it is on my TODO list to make this work 
better, but in the absence of good documentation of what the Excel ODBC 
driver should do and several with known bugs it is largely a matter of 
trial-and-error.

On Tue, 27 Mar 2007, Moshe Olshansky wrote:

> Dear Prof. Ripley,
>
>> You seem not to have tried the simplest possible option.  The following
>> works for me (beware of wrapped lines from mailers)
>>
>> chan <- odbcDriverConnect("DRIVER=Microsoft Excel Driver (*.xls);DBQ=C:\\bdr\\hills.xls; ReadOnly=False")
>> sqlSave(chan, USArrests, "tests", fast=TRUE) # or FALSE
>
> You are right - I have not.
> It does not work exactly as it should have but this solves my problem.
> I created a very small Excel file odbc1.xls containing 3 sheets (test, Sheet2 and Sheet3).
> Below is a short R session:
>
>> chan <- odbcDriverConnect("DRIVER=Microsoft Excel Driver (*.xls);DBQ=C:\\EFGraphs\\odbc1.xls; ReadOnly=False")
> >x<- c(1:6)
> >x <- matrix(x,nrow=3,ncol=2)
> >x <- data.frame(x)
> x
>  X1 X2
> 1  1  4
> 2  2  5
> 3  3  6
>> sqlSave(chan, x, "test", fast=FALSE)
> Error in sqlSave(chan, x, "test", fast = FALSE) :
>        table 'test' already exists
>> sqlSave(chan, x, "tests", fast=FALSE)
>
> As you see I was unable to overwrite an existing sheet (an attempt to drop this table also fails), but I was able to add a new sheet to an existing Excel file (after this action the file contains 4 sheets - the 3 it contained and the last sheet named tests).
> This allows me to do what I wanted, i.e. manually create an Excel file with a small VBA macro, make many copies of this file (under appropriate names), write an appropriate data to each file and then the macro will work on the right data (different for each file).
>
> Thanky you!
>
> Moshe.
>
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> Moshe Olshansky
>
> Chimaera Capital Limited
> Level 4 / 349 Collins Street
> Melbourne, Victoria 3000
> Phone: +613 8614 8400
> Fax: +613 8614 8410
> Email: molshansky at chimaeracapital.com
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595