remove contour points

Hello,

In the contour function,

[C,D] = contour(x,y,Z)

C = [ value1 xdata(1) xdata(2)... numv ydata(1) ydata(2)...]

where value1 is the value of the contour, numv is the number of points on that contour, and xdata/ydata specify that point on the plot.

Is there a way to remove, say, all xdata < 0.3 and then replot the subsequent contour?

Thank you!