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Plot Magic Voodoo ???

  • To: mathgroup at
  • Subject: [mg90930] Plot Magic Voodoo ???
  • From: beckman <bc.beckman at>
  • Date: Wed, 30 Jul 2008 03:52:13 -0400 (EDT)

Consider the following:

z := {L == x y, y == x, x == y}

Solve[z, {L}] --->  {{L->y^2}}

no surprises. now,

Plot[L /. Solve[z, {L}][[1]], {y, 1, 10}]

Works exactly as one would expect, BUT, this also works

Plot[L /. Solve[z, {L}][[1]], {x, 1, 10}]

BUT, the first argument of Plot is L /. Solve[z, {L}][[1]], which is
y^2, so my brain said that

Plot[L /. Solve[z, {L}][[1]], {x, 1, 10}] ---> Plot[y^2, {x, 1, 10}]

which, of course, cannot work. Btw,

Plot[L /. Solve[z, {L}][[1]], {q, 1, 10}]

does not work, so SOMEHOW, Plot is magically peeking at the innards of
the Solve expression, and is NOT evaluating it, and noticing that x is
a free variable in the set of equations, z, and ... my brain is

would someone be so kind as to shed some light on this voodoo, please
and thanks?

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