Re: Drawing a Line From One Plot to Another

• To: mathgroup at smc.vnet.net
• Subject: [mg127702] Re: Drawing a Line From One Plot to Another
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Wed, 15 Aug 2012 03:38:06 -0400 (EDT)
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• References: <20120814082121.B6E906849@smc.vnet.net>

```It might be easier to use a single plot with one function offset. That
would keep you in a single set of coordinates.

y1[x_] = x^2;
y2[x_] = 2 x;

pts = {x, y1[x]} /.
Solve[y1[x] == y2[x], x];

offset = 10;

plt = Plot[
Evaluate[
{Tooltip[y1[x]] ,
Tooltip[y2[x] - offset, y2[x]]}],
{x, -1, 3},
Frame -> True,
Axes -> False,
Epilog -> {
Text[#, #, {1, -2}] & /@ pts,
Text[# + {0, offset}, #, {-1, 2}] & /@
((# - {0, offset}) & /@ pts),
{Thick, Line[{{-1.5, -2}, {3.5, -2}}]},
Red, AbsolutePointSize[4],
Point[pts],
Point[(# - {0, offset}) & /@ pts],
Darker[Green],
AbsoluteDashing[{10, 5}],
Arrow[{#, # - {0, offset}}] & /@ pts}];

Show[plt, FrameTicks -> {
Automatic,
(FrameTicks /.
AbsoluteOptions[plt, FrameTicks])[[2]] /.
{y_, yl_?(NumericQ[#] && # < -1 &), r___} ->
{y, yl + offset, r}}]

However, it may be easier still to plot the multiple functions on the
same plot. If necessary use two separate y axes (right and left frame
axes).

Plot[
Evaluate[
Tooltip /@
{y1[x] , y2[x]}],
{x, -1, 3},
Frame -> True,
Axes -> False,
Epilog -> {
Text[#, #, {-1, 2}] & /@ pts,
Red, AbsolutePointSize[4],
Point[pts]}]

Bob Hanlon

On Tue, Aug 14, 2012 at 4:21 AM, Gregory Lypny
<gregory.lypny at videotron.ca> wrote:
> Hello everyone,
>
> Say I have two plots, y=x^2 and y=2x, aligned vertically using GraphicsColumn.  Their domains are aligned because x runs from -3 to +3 in both. I'd like to be able to draw a line from a point in the top graph to a point in the bottom graph.  How can I do that?
>
> Regards,
>
> Gregory
>

```

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