I want to do a time series plot but how can i solve the error below?

> x> x(x, frequency=4, start=c (1980,1) ) > ts.plot (x.main="Wasington Water Power Co") Error in plot. window(xlim, ylim, log, ...) : need finite 'ylim' values In addition: Warning messages: 1: In xy.coords(x, NULL, log =log, setLab = FALSE) : NAs introduced by coercion 2: In min (x) : no non-missing arguments to min; returning Inf 3: In max (x) : no non-missing arguments to max; returning -Inf