Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2001
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2001

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: making a function of two coordinates

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31638] Re: [mg31617] making a function of two coordinates
  • From: Anton Antonov <antonov at wolfram.com>
  • Date: Mon, 19 Nov 2001 03:11:22 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

	Hi Roderik,
	First for the exponential you can use the Mathematica build-in
function Exp[]. Also, equations in Mathematica are defined in with ==.
So this is OK:

In[1]:= Clear[U, e, a, t, y]
        Solve[y == U*Exp[a*t], a]

Out[1]:={{a -> Log[y/U]/t}}

	I used Clear[] because y = U*e^(a*t) sets a value to y.
(Try to evaluate  y = U*e^(a*t) first and then Solve[y == U*e^(a*t), a],
and you will see that nothing happens.) If you try

In[2]:= Solve[y == U*e^(a*t), a]

you will get

Out[2]:= {{a -> Log[y/U]/(t*Log[e])}}

since Mathematica doesn't know what e is.

	Best,
	Anton

==============================================================
Anton Antonov Antonov, PhD     *****     Wolfram Research Inc.
http://www.imm.dtu.dk/~uniaaa   ***   tel +1 217 398 0700 #782
==============================================================
               Give me wings and I will crawl faster!
--------------------------------------------------------------

On Sun, 18 Nov 2001, TheSquaredBun wrote:

>
> I have got two coordinates out of graph. The line through the
> coordinates could be described as:
>
> y = U * e^(a * t)
>
> (e is Exponetial e (approx. 2.37))
>
> t is the x-value, I have give two points (t1,y1) and (t2,y2)
>
> I have tried several things (Solve and Fit for example), but I can't
> get the function.
> Does anyone know what should be the input to let Mathematica solve the
> a and U in the formula.
>
> Much thanks in advance,
>
> Roderik
> r.f.emmerink at st.hanze.nl
>



  • Prev by Date: Re: Creating objects
  • Next by Date: Evaluate Initialization button?
  • Previous by thread: Re: making a function of two coordinates
  • Next by thread: Evaluate Initialization button?