On Mon, Jun 22, 2015 at 11:14 PM, Tatsuro MATSUOKA <address@hidden> wrote:
----- Original Message -----
>From: Ariana del Tor
>To: Cinthia Mesquita Pinke Cavalcanti
>Cc: "help
>Date: 2015/6/23, Tue 09:22
>Subject: Re: Polynomial interpolation
>
>
>http://www.mathworks.com/help/matlab/ref/polyfit.html
>
>Please see the first example. You need to feed polyfit two vectors, x and y of the same size.
>
>
>so define x and y separately in your case it looks like:
>
>
> x = [1, 2, 3, 4, ....]
>y = [ 73, 99, 90, 24...]
>
>
>
>and finally n is the number of points you want to fit the array to. n can equal up to # of point - 1.
>
>
>On Mon, Jun 22, 2015 at 1:15 PM, Cinthia Mesquita Pinke Cavalcanti <address@hidden> wrote:
>
>Dear Sir/ Madam
>>
>>I am new to Octave, and I was not able to work with the polyfit function.
>>I have the matrix listed below and I want to find the polynomial coefficients that fit to the points x,y:
>>
>>
>>What should I do?
>>
>>Thanks in advance,
>>
>>
>>Cínthia Pinke
>>
>Ariana del Toro
>DATA ANALYST
>address@hidden
Note
polyfit is not a function for polynomial interpolation but a function of
polynomial curve fitting.
Wiki
polynomial interpolation
https://en.wikipedia.org/wiki/Polynomial_interpolation
Curve fitting
https://en.wikipedia.org/?title=Curve_fitting
Tatsuro
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Here is one example with N=5
You can try other values.
x = [1, 2, 3, 4,5,7,8,9,10,11,12];
y = [ 73, 99, 90, 24,18,25,16,31,32,74,92];
p=polyfit(x,y,5)
xx=0:.1:13;
v=polyval(p,xx);
plot(xx,v,x,y,'o')