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MathGroup Archive 2004

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RE: Function interpolation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg45368] RE: [mg45336] Function interpolation
  • From: "tgarza01 at prodigy.net.mx" <tgarza01 at prodigy.net.mx>
  • Date: Sat, 3 Jan 2004 01:35:10 -0500 (EST)
  • Reply-to: tgarza01 at prodigy.net.mx
  • Sender: owner-wri-mathgroup at wolfram.com

First, you are using the name Table which is a Mathematica in-built
function for a list of numbers defined by you. Use any other (non-reserved)
name. Second, you have to respect the syntax of parentheses and brackets.
Then,
 
In[1]:=
otherName = {{0, 0}, {1, 2}, {2, 4}, {3, 8}, {4, 16}, 
    {5, 32}}; 

In[2]:=
newfunction = Interpolation[otherName]
Out[2]=
InterpolatingFunction[]

In[3]:=
newfunction[2.3]
Out[3]=
4.899

In[4]:=
Plot[{newfunction[x], Derivative[1][newfunction][x]}, 
  {x, 0, 5}]

Tomas Garza
Mexico City

Original Message:
-----------------
From:  fernandoronci at hotmail.com (Fernando Ronci)
To: mathgroup at smc.vnet.net
Subject: [mg45368] [mg45336] Function interpolation


Hi,

I'm new to Mathematica and need some hints on how to derive (or
estimate) a function from a given set of discrete x/y values.
I know Mathematica can do this but I don't know how.
For example, I tried to create a table of x/y values, then assign the
approximated funcion to 'newfunction' and test it by calling it with
2.3 as argument, but it failed as follows (I couldn't even figure out
how to build the table):

Table = [{0, 0}, {1, 2}, {2, 4}, {3, 8}, {4, 16}, {5, 32}]
newfunction = Interpolation[%]
newfunction[2.3]

Syntax::"sntxf": "Table =" cannot be followed by "[{0, 0}, {1, 2}, {2,
4}, {3, 8}, {4, 16}, {5, 32}]".
Table = [{0, 0}, {1, 2}, {2, 4}, {3, 8}, {4, 16}, {5, 32}]

BTW, I'm working with Mathematica 4.
Help appreciated.
Thank you,

Fernando Ronci
E-mail: fernandoronci at hotmail.com


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