# Why doesn't this plot work?

I'm trying to plot the output of an integral, but the plot does not show. The axes show, but not the plot itself. I have tried what I felt was a reasonable range of axes values, but the result is the same. The following is what I'm working with:

function = Exp[I k x] C Exp[-a x^2];

Integrate[function, {x, -\[Infinity], \[Infinity]}]

ConditionalExpression[(C E^(-(k^2/(4 a))) Sqrt[\[Pi]])/Sqrt[a],
Re[a] > 0]

output = %;

Plot[output, {k, -10, 10}]


What is wrong here? Anyone have some suggestions on how to obtain the plot? I'm compelled to think there is some kind of 'automatic' range parameters that can be used with general plots, but I have not found anything in the Documentation center of Mathematica, nor have I found any FAQs here that I've found helpful either.

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I'm almost sure I've seen several questions like these, but can't find them at the moment. –  Sjoerd C. de Vries Sep 27 '12 at 19:11

It is because C and a are undefined; if they are set to something, a plot is obtained, e.g.

function = Exp[I k x] C Exp[-a x^2];
Integrate[function, {x, -\[Infinity], \[Infinity]}]
% /. {a -> 3, C -> 5}
Plot[%, {k, -10, 10}]


gives

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Thanks Renan... I wondered if that's what it was about, but I guess I assumed Mathematica would 'choose' generic values such that a basic plot would show within the parameters I gave to it. Thank You! –  fiz Sep 27 '12 at 19:06
@fiz you're welcome; if this solved the problem, please accept this answer. –  Renan Sep 27 '12 at 20:02
Hi Renan....Maybe this sounds dumb...I'm fine with your answer....but how do I 'Accept" your answer? Is that something specific? This is NOT a uer-friendly site to navigate in my opinion. I'm new....don't get to spend a lot of time here. –  fiz Sep 28 '12 at 0:39
@fiz read the FAQ: mathematica.stackexchange.com/faq#howtoask –  Renan Sep 28 '12 at 1:29
Thanks...got it. I'm a work in progress, now I need to go back to other questions I've asked and do this too. I was not aware and missed it in reading thru the site. –  fiz Sep 28 '12 at 12:26