[R] RODBC, sqlQuery with NA:s

[Prof Brian Ripley]

In my attempts to reproduce this both approaches worked.

There seems to be something going on we cannot see (and I don't believe 
NULL in the database is being mapped to " ").  For example, might there be 
non-breaking spaces (character A0 in Windows 1252, your most likely 
character set) in the database?

On Mon, 2 Apr 2007, Lauri Nikkinen wrote:

> Hi R-users,
>
> I'm trying to retrieve data from MS SQL database with RODBC's
> sqlQuery-function:
>
> temp <- sqlQuery(channel,"select *, (select text from table1 where
> koodi='paa' and koodi2=paa) as tempor from table2")
>
> str(temp)
>
> 

> $ var0        : num  NA NA 1.6 NA NA 1.4 NA 1 NA NA ...
> $ var1          : Factor w/ 45 levels " ","01","01;07",..: 1 1 1 4 38 1 38 7
> 1 1 ...
> $ var2        : Factor w/ 95 levels " ","01","01;02;09",..: 1 1 1 9 72 1 78
> 13 1 1 ...
> $ var3      : Factor w/ 104 levels " ","01","01;02;09",..: 1 1 1 44 82 1 87
> 14 1 1 ...
> 

>
> Data types of these variables in the MS SQL database are:
>
> var0: float, NULL
> var1: varchar, NULL
> var2: varchar, NULL
> var3: varchar, NULL
>
> As you can see from above, I get variable var0 with NA:s because of the data
> type (there is NULL in the database if there is no observation in the
> specific cell). How can I get NA:s to these Factor variables also? I have
> tried the following with no positive results:
>
> temp <- sqlQuery(channel,"select *, (select text from table1 where
> koodi='paa' and koodi2=paa) as tempor from table2", na.strings=" ")
>
> and also afterwards
>
> temp$var1[temp$var1 == " "] <- "NA"
>
> Regards,
> Lauri
>
> 	[[alternative HTML version deleted]]
>
>

-- 
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)
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