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> please note that i don't want to connect two known points. i want
> to draw a parallel line through a known trend line or pair of
> points.
If you know two points, it should be pretty easy. If your points are
X1,Y1 and X2,Y2, then why not draw a line from X1+Z,Y1 to X2+Z,Y2?
That draws the trendline Z units vertically above the existing line.
If you want the parallel line to be a specific distance away from the
trendline, say H (for Hypotenuse :-), then you just need to do a
little trig.
The angle of the trendline is
theta = arctangent((Y2-Y1)/(X2-X1)).
Theta is also the angle between a vertical line and a line
perpendicular to your trendline. So
Z = H * cosine(theta)
This is off the top of my head but I think it's right...
(View this in a fixed-pitch font like Courier:)
. X2+Z,Y2
.
.
.
.
.
. | . X2,Y2
. \ | .
. \ | Z .
X1+Z,Y1 H \ | .
\| .
.
.
. theta
X1,Y1 . ----------------
Gary
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