PSYM=0 does nothing, and there is never any reason to use it. The only reason the line you are seeing should be drawn "from the last data point" is if there were one additional datapoint described in your x and y arrays that you did not expect to be there, one that has a 0 value for x and a y value equal to the second-to-last value in the y array. Thus, I would query to see what the values of x and y are at subscripts [0:1] and at subscripts [n_elements(x)-2:n_elements(x)-2]] and/or I might try to: PLOT, x[1:n_elements(x)-2], y[1:n_elements(x)-2] just to see what happens if I get rid of the endpoints. James Jones