R help - Nov 2004 - Odd behaviour of R 2.00

Dear R users

I have a data frame containing character and numeric variables, whose
name is seishin.  When I tried to assign NA to "" in the data frame,
R, 2.00
showed an error message, such as
> seishin[seishin==""]<-NA
Error: NAs are not allowed in subscripted assignments

This did not happen under R 1.9.0.

More oddly,
The following commands work just fine under R 2.0.0
> a<-1:10
> b<-letters[1:10]
> b[3]<-""
> c<-data.frame(cbind(a,b))
> c[c==""]<-NA
Why is this so?
And how can I assign NA to "" data.framewise in seishin data.frame?
Please help.

Sincerely
--------------------------------
Hiroto Miyoshi
h_m_ at po.harenet.ne.jp

"Hiroto Miyoshi" <h_m_ at po.harenet.ne.jp> writes:
> Dear R users
> 
> I have a data frame containing character and numeric variables, whose
> name is seishin.  When I tried to assign NA to "" in the data
frame, R, 2.00
> showed an error message, such as
> 
> > seishin[seishin==""]<-NA
> Error: NAs are not allowed in subscripted assignments
> 
> This did not happen under R 1.9.0.
> 
> More oddly,
> The following commands work just fine under R 2.0.0
> > a<-1:10
> > b<-letters[1:10]
> > b[3]<-""
> > c<-data.frame(cbind(a,b))
> > c[c==""]<-NA
> 
> Why is this so?
It is the NA pattern on the left hand side that matters. Does it help
to use 

seishin[!is.na(seishin) & seishin==""]<-NA

?

(For atomic vectors you could also use %in% instead of ==, but this
doesn't work with data frames.)
> And how can I assign NA to "" data.framewise in seishin
data.frame?
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