Lowest year among several variables

testdata <- read.table("clipboard", header=TRUE)
apply(testdata, 1, function(x)if(all(x == 0)) {0} else {min(x[x > 0])})

...still new to R and trying to figure this one out.

I have a number of variables x, y, z, etc. in a data frame.

Each contains a 2 digit year (e.g., 80, 81, 82) representing the first year
that something occurred. Each variable represents a different type of event.

If the event did not occur at all, the variable has the value 0 (zero).

I need to create a new variable having the value of the earliest year among
the set of variables.

If none of the events occurred (all variables = 0), then the new variable
should also be zero.

e.g.,

Original
x ? ?y ? z
80 82 83
85 ?76 ?90
90 ?0 ? 86
0 ? 0 ? 0


New variable
80
76
86
0