R help - Apr 2011 - if else statements in data frame

Dear R experts, I have again a problem. Let I have a data frame like below:

x	y
----------
A	A
A	B
B	B
A	B

where x and y are the column names. I want to create a new column z where it
is elements
will be like that, if at each row has there at least one 'B', then z
will
have value of B, if not then Z will
have missing value(NA) for the corresponding row. So my result data frame
should be like below:

x	y	Z
------------------
A	A	NA
A	B	B
B	B	B
A	B	B

How can I do this with if else statements in R. Thanks a lot.   


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Hi ozgrerg,

I am not a "good" R user, but according to me you can do this;

data <-
data.frame(x=c("A","A","B","A"),
y=c("A","B","B","B"))
for (i in 1:nrow(data)){
if(data$x[i]=="B"||data$y[i]=="B") z[i]=c("B")
else
z[i]=c("NA")
}

cbind(data,z)

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Thanks for the answers. They were very helpful. I did it like below.

data$z <- ifelse(data$x == "A" & data$y == "A",
"NA", "B").

That is enough for today. I guess I learned a enough today. Thanks to
everbody who tried to help. 




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Thanks  alot B77S. That was a critical post. 

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