R help - Nov 2009 - shrink list by mathed entries

Hello

a <- c("Mama", "Papa", "Papa; Mama",
"", "Sammy; Mama; Papa")
a <- strsplit(a, "; ")
mama <- rep(F, length(a))
mama[sapply(a, function(x) { sum(x=="Mama") }, simplify=T) > 0]
<- T
papa <- rep(F, length(a))
papa[sapply(a, function(x) { sum(x=="Papa") }, simplify=T) > 0]
<- T
# ... more variables

... produces the variables "mama" and "papa" correctly. But
how do I
remove all "Mama" list entries in "a" in the same run, that
is, shrink
the list by what was already matched?

Thank you for your help!

S?ren Vogel


-- 
S?ren Vogel, Dipl.-Psych. (Univ.), PhD-Student, Eawag, Dept. SIAM
http://www.eawag.ch, http://sozmod.eawag.ch

On Nov 13, 2009, at 11:19 AM, Soeren.Vogel at eawag.ch wrote:
> Hello
>
> a <- c("Mama", "Papa", "Papa; Mama",
"", "Sammy; Mama; Papa")
> a <- strsplit(a, "; ")
> mama <- rep(F, length(a))
> mama[sapply(a, function(x) { sum(x=="Mama") }, simplify=T) >
0] <- T
> papa <- rep(F, length(a))
> papa[sapply(a, function(x) { sum(x=="Papa") }, simplify=T) >
0] <- T
> # ... more variables
>
> ... produces the variables "mama" and "papa" correctly.
But how do I
> remove all "Mama" list entries in "a" in the same run,
that is,
> shrink the list by what was already matched?
Maybe you should explain what you were trying to do?  Perhaps:

 > a[!mama]
[[1]]
[1] "Papa"

[[2]]
character(0)

I would sidestep that confusing sequence of logical assignments and  
just do this:

 > a[ -grep("Mama", a) ]
[[1]]
[1] "Papa"

[[2]]
character(0)
>
-- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT