       Re: changing variable in an equation

• To: mathgroup at smc.vnet.net
• Subject: [mg116378] Re: changing variable in an equation
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Sat, 12 Feb 2011 05:20:22 -0500 (EST)
• References: <201102110917.EAA07980@smc.vnet.net>

```You have a missing parenthesis, so I'll have to guess where you wanted it.

Your three examples don't seem to match the phrase "working from -100 to
100".

And there's a third variable -- x -- that you haven't explained. I'll give
it a fixed value.

So... working from -10 to t+10 to save time, and t varying from 0 to .1 so
that everything isn't obscured by the scale:

Clear[v]
v[i_, x_, t_] = -67 + (10 (i - 1) + 67) x E^(-19 x t)/10;
x = 3;
Plot[Evaluate@Table[v[i, x, t], {i, -10, 10}], {t, 0, .1},
PlotRange -> All]

In case it's x that should vary from -100 to 100, then I don't know what
values i should take on.

But... if you want to vary both, here's an example:

Plot[Evaluate@Table[v[i, x, t], {i, -10, 10}, {x, 0, 3}], {t, 0, .1},
PlotRange -> All]

Notice that this is colored differently:

Plot[Table[v[i, x, t], {i, -10, 10}, {x, 0, 3}], {t, 0, .1},
PlotRange -> All]

That's what Evaluate is about, in the other plots.

Bobby

On Fri, 11 Feb 2011 03:17:10 -0600, J and B <noslowski at comcast.net> wrote:

> Below is an equation that I am working on. I know there is some way to
> work
> it out better than what I am doing.  I would like the variable a to
> change
> in increments of 10, from -100 to 100.
> Thanks
> my main equation is:  v = -67+(a-(-67) x E ^ (-19 x t)/10
> what I am doing:
> v1= -67+(0-(-67) x E ^ (-19 x t)/10;
> v2= -67+(-10-(-67) x E ^ (-19 x t)/10;
> v3= -67+(-20-(-67) x E ^ (-19 x t)/10;
> and so on and working from -100 to 100
> Then I use
> Plot [ { v1,v2, v3 ........},{t,0,5}, PlotRange -> All]