R help - Jan 2005 - Targeting the elements that satisfy matching rules excluding the NA

Dear R-List,
here my problem:
> a <-
c("gio","gao","geo",NA,"1","alpha")
> b <- 1:6
> data.frame(V1=a,V2=b) -> c
> c
     V1 V2
1   gio  1
2   gao  2
3   geo  3
4  <NA>  4
5     1  5
6 alpha  6
> rownames(c) %in% grep("a",as.character(c$V1))
[1] FALSE  TRUE FALSE FALSE FALSE  TRUE

while I would like to obtain
[1] FALSE  TRUE FALSE <NA> FALSE  TRUE

Is there a simple way to do this without doing things
like
> rownames(c) %in% grep("a",as.character(c$V1)) -> tmp
> tmp[is.na(c$V1)]<- NA
?

It would be nice if grep (or another command) produced FALSE or TRUE according 
to the matching rule and NA if the value is NA. I was not able to find such a 
feature (just to do this in one simple command-line :)).

Thank you,
Giovanni Malerba.

Giovanni Malerba <bobo <at> medgen.univr.it> writes:

: 
: Dear R-List,
: here my problem:
: > a <-
c("gio","gao","geo",NA,"1","alpha")
: > b <- 1:6
: > data.frame(V1=a,V2=b) -> c
: > c
:      V1 V2
: 1   gio  1
: 2   gao  2
: 3   geo  3
: 4  <NA>  4
: 5     1  5
: 6 alpha  6
: 
: > rownames(c) %in% grep("a",as.character(c$V1))
: [1] FALSE  TRUE FALSE FALSE FALSE  TRUE
: 
: while I would like to obtain
: [1] FALSE  TRUE FALSE <NA> FALSE  TRUE
: 
: Is there a simple way to do this without doing things like
: > rownames(c) %in% grep("a",as.character(c$V1)) -> tmp
: > tmp[is.na(c$V1)]<- NA
: ?
: 
: It would be nice if grep (or another command) produced FALSE or TRUE 
according 
: to the matching rule and NA if the value is NA. I was not able to find such 
a 
: feature (just to do this in one simple command-line :)).
: 


regexpr("a", as.character(c$V1)) > 0

Hi Giovanni

I am not sure if it is the correct way but

regexpr("a",as.character(df$V1))>0
[1] FALSE  TRUE FALSE    NA FALSE  TRUE

gives me the logical vector you would like to see.

Cheers
Petr

On 5 Jan 2005 at 19:16, Giovanni Malerba wrote:
> Dear R-List,
> here my problem:
> > a <-
c("gio","gao","geo",NA,"1","alpha")
> > b <- 1:6
> > data.frame(V1=a,V2=b) -> c
> > c
>      V1 V2
> 1   gio  1
> 2   gao  2
> 3   geo  3
> 4  <NA>  4
> 5     1  5
> 6 alpha  6
> 
> > rownames(c) %in% grep("a",as.character(c$V1))
> [1] FALSE  TRUE FALSE FALSE FALSE  TRUE
> 
> while I would like to obtain
> [1] FALSE  TRUE FALSE <NA> FALSE  TRUE
> 
> Is there a simple way to do this without doing things like
> > rownames(c) %in% grep("a",as.character(c$V1)) -> tmp
> > tmp[is.na(c$V1)]<- NA
> ?
> 
> It would be nice if grep (or another command) produced FALSE or TRUE
> according to the matching rule and NA if the value is NA. I was not
> able to find such a feature (just to do this in one simple
> command-line :)).
> 
> Thank you,
> Giovanni Malerba.
> 
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Petr Pikal
petr.pikal at precheza.cz