Can I combine points in a scatter diagram without drawing by hand
 

I have made a line diagram with several series. The problem is that the
different series don't have the same X values (it's different sampling
dates), and when an X value is skipped for a serie (ex. dates 3/12, 5/12 och
9/12, where I only have Y values for the first and last date), the line
diagram won't draw a line between my 2 Y values (that correspont to to the X
values 3/12 and 9/12). I have a lot of data to work with, and now I draw
lines between all points by hand. And that takes a LOT of time. Is there a
better way???

Best regs,

/Anna