Why doesn't my Manipulate work?

Question

I am new to Mathematica and reading my way through a few books. Playing around with Manipulate and I noticed the following does not work:

y[x_]:=x^n;
plot := Plot[y[x],{x,0,10}, AspectRatio->1];
Manipulate[plot,{n,1,5}]

I expected the above to work as I am using SetDelayed in my function definition so not sure if I understand why this doesn't work.

However the following does work.

Manipulate[
 Module[{y,x,plot},
  y[x_]:=x^n;
  plot := Plot[y[x],{x,0,10}, AspectRatio->1];
  Show[plot] 
 ],
 {n,1,5}
]

Please have a look at the markdown page and format your question to allow for easy reading (Indenting code segments by four spaces already helps a lot). — Yves Klett, Jan 31 '13 at 15:57
@YvesKlett I was going for quick, and a gold badge (eventually). :) — rcollyer, Jan 31 '13 at 15:58
I didn't realise you got points and badges for editing questions. I thought everyone did it for the greater good... :) — cormullion, Jan 31 '13 at 17:14

score 6 · Answer 1 · answered Jan 31 '13 at 18:51

6

Your problem stems from the n in y[x_] := x^n; not being in the same scope as the n in your Manipulate and, therefore, not being the same variable.

The following modified version works as you were expecting:

plot[n_] := Plot[x^n, {x, 0, 10}, AspectRatio -> 1];
Manipulate[plot[n], {n, 1, 5}]

answered Jan 31 '13 at 18:51

m_goldberg

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Thanks, didn't think of that. Much appreciated. – David McHarg Jan 31 '13 at 19:31

Why doesn't my Manipulate work?

1 Answers1

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