[R] Accessing values of a matrix

[statquant]

Hello Sarah, thanks for answering
For example if I have the following example 

 test <- as.data.frame(matrix(c(1,2,3,4, 11,12,13,14, "a","b","b","c"), nrow
= 3, ncol=3,dimnames = list(c("r1","r2","r3","r4"),NULL))

   V1 V2 V3
r1  1 11  a
r2  2 12  b
r3  3 13  b
r4  4 14  c

it is easy to select test <- test[,mylist] with for example mylist <-
c("V1","V3")

   V1 V3
r1  1  a
r2  2  b
r3  3  b
r4  4  c

But after how can I restrict test in selecting the rows where the result in
column V3 are in a list mylist2, with for example mylist2 <-c("b","c","d") ?
which would give as an example 

   V1 V3
r2  2  b
r3  3  b
r4  4  c

Regards 
Colin
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