[R] Subsetting by a logical condition and NA's

[John Miyamoto]

I have run into a general problem with subsetting of which the following
is a simple example.  Suppose that

x <- c(5, NA, 7, 5, NA, 3)
y <- c(1,  2, 3, 4,  5, 6)

I want to extract the values of y for which x = 5, but y[x==5] yields

> y[x==5]
[1]  1 NA  4 NA

I find that y[!is.na(x) & x==5] yields the desired result:

> y[!is.na(x) & x==5]
[1] 1 4

but I am wondering whether there is a general way to specify a logical
condition such that it yields TRUE when the condition is true and FALSE
when the condition is either false or the input data is NA?  For example,
is there a simpler way to produce the same results as y[!is.na(x) & x==5]?

John

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John Miyamoto, Dept. of Psychology, Box 351525
University of Washington, Seattle, WA 98195-1525
Phone 206-543-0805, Fax 206-685-3157, Email jmiyamot at u.washington.edu
Homepage http://faculty.washington.edu/jmiyamot/
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