gnuplot conditional plotting: plot col A:col B if col C == x

http://stackoverflow.com/questions/6564561/gnuplot-conditional-plotting-plot-col-acol-b-if-col-c-x

How can I do this in gnuplot:

plot "test.csv" using 1:2 if value_in_column_3 == 80.0

It should only select those rows where column 3 == 80.0 and ignore all other rows (It should not plot a 0 for the other rows, simply ignore them)

Thanks in advance.