Re: How to plot functions

• To: mathgroup at smc.vnet.net
• Subject: [mg130117] Re: How to plot functions
• Date: Sun, 10 Mar 2013 17:07:52 -0400 (EDT)
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• References: <khh6p6\$ako\$1@smc.vnet.net>

```You need an underscore to indicate that c is a variable.

f[c_]:=c x^2

Plot[f[3],{x,-10,10}]

It is also a good idea to make x a variable, like this.

Clear[f]

f[x_,c_]:=c x^2

Plot[f[x,3],{x,-10,10}]

Manipulate[Plot[f[x, c], {x, -10, 10}, PlotRange -> 500], {c, -5, 5}]

Or like this.

Clear[f]

f[c_][x_] := c x^2

Plot[f[3][x], {x, -10, 10}]

Manipulate[Plot[f[c][x], {x, -10, 10}, PlotRange -> 500], {c, -5, 5}]

I prefer this latter style of notation if I am thinking of one of the
variables (here c) as a subscript or parameter, as opposed to defining a
multivariate function that I would plot with Plot3D.

University of Vermont

On 3/10/2013 12:47 AM, radres wrote:
> Hi,
>
> Let's say I've defined a function f[c]=c*x^2
>
> when I try to plot this directly,
>
> Plot[ f[3], {x, -10, 10} ]
>
> it doesn't plot anything.
>
> But when I assign function to a variable,
>
> v1=f[3]; Plot[v1, {x, -10, 10}]
>
> then there is no problem. But I dont want this. Is there any way to plot directly from a function?
>

```

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