Draw a line in line chart

[nvijay5757]

Hi 

i am trying to draw a line in line chart but it is showing  a point in that position.

please help me x- axis: 8, y-axis: y1,y2: (-170,-170)

in this i need to draw-  Sev1-set1 vs set2   and     D Vs ND    line to draw please help me. i am getting only one dot at that position.

Thanks