Can anyone explain why the below code does not produce a plot?
Clear["Global`*"]
f[x_, a_] = a - x^2;
Solve[f[x, a] == x, x]
Manipulate[ Plot[{f[x, a], x}, {a, -2, 2}], {a, 1, 20, Appearance -> "Labeled"}]
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2 Answers
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f[x_, a_] = a - x^2;
Manipulate[
Plot[{f[x, a], x},
{x, -5, 5},
PlotRange -> {{-5, 5}, {-5, 5}},
Epilog -> {Red, PointSize[0.02], Point[{x, f[x, a]} /. # & /@ Solve[f[x, a] == x, x]]}
],
{a, 1, 20, Appearance -> "Labeled"}]
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$\begingroup$ OP here. I had to log into the correct account. Sorry for the confusion in my post. I'm not familiar with how the end of the
Epilogline works. That is, what does ` /. # & /@ ` do? I am inferring that this places a red point where I have a fixed point, but i'm still curious. And thank you for the help! $\endgroup$– OzeraCommented Feb 24, 2016 at 0:56 -
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/.is shorthand Infix notation forReplaceAll./@is Infix notation forMap.#isSlot[1]which is used for defining a pure function with&is the short-hand forFunction. You can look up all of these in the documentation. $\endgroup$– marchCommented Feb 24, 2016 at 0:58 -
$\begingroup$ Okay. Thank you for the information. Since I am not in the original account I posted in (my mistake), I supposed i'll just say: POST RESOLVED ?Maybe I can ask a moderator to accept this post? $\endgroup$– OzeraCommented Feb 24, 2016 at 1:01
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$\begingroup$ @Ozera. You should be able to merge accounts, perhaps by contacting a moderator. $\endgroup$– marchCommented Feb 24, 2016 at 3:03
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$\begingroup$ @Ozera, please see this for help with merging your accounts. $\endgroup$ Commented Feb 24, 2016 at 10:23
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With a few bells and whistles.
Clear[f]
f[x_, a_] = a - x^2;
soln[x_, a_] = Solve[f[x, a] == x, x];
Manipulate[
Column[{
Plot[{f[x, a], x}, {x, -2, 2},
Epilog -> {Red, AbsolutePointSize[5],
Point[{x, f[x, a]} /. soln[x, a]]},
ImageSize -> 360,
PlotLegends -> Placed[{f[x, a], x}, {.7, .2}]],
StringForm["\nx = ``", Or @@ (x /. soln[x, a])]},
Alignment -> Center],
{{a, 0}, -0.25, 2, .05,
Appearance -> "Labeled"}]
answered Feb 24, 2016 at 1:28
Solvedoesn't set the value ofx, so you are trying to plot something that has the parameterxin it with no value plugged in forx. You also have some scoping problems, I think, where thea's aren't actually the same. It's actually pretty unclear what you're actually trying to do here. Can you add some explanations to your post? $\endgroup$x, not fora. Change to :Manipulate[ Plot[{f[x, a], x}, {x, -2, 2}], {a, 1, 20, Appearance -> "Labeled"}]$\endgroup$