I use the following code to generate four plots in a window. However, in the subwindow 0, only the curve Y2 is plotted, which means that the curve Y1 is erased, while the other plots are correct in the subwindow 1, 2, and 3 Window, 0, XSIZE=1000, YSIZE=800 !P.MULTI = [0,2,2] Plot, Y1, /NOERASE Plot, Y2, COLOR=255 Plot, Y3, /NOERASE Plot, Y4, COLOR=255 Plot, Y5, /NOERASE Plot, Y6, COLOR=255 Plot, Y7, /NOERASE Plot, Y8, COLOR=255