Register to reply

Curve fitting using matlab

by hunter55
Tags: curve, fitting, matlab
Share this thread:
hunter55
#1
Nov8-08, 11:18 PM
P: 3
1. The problem statement, all variables and given/known data
For the given set of data, find the least-square curve:
A) f(x)=Ce^Ax, by using the change of variable X=x, Y=ln(y), and C=e^B to linearize the data points.

B) f(x) = 1/(Ax+B), by using the change of variable X=x and Y = 1/y to linearize the data points.

x : [ -1 0 1 2 3]
y : [ 6.62 3.94 2.17 1.35 0.89]

I need the matlab code on how to do these 2 problems im confused and which curve gives a better fit. ??


2. Relevant equations

This is the only code i know but idk how to do it with the question they are asking i need to pertain it to that

function C = poly(X,Y,M)
n=length(X);
B=zeros(1:M+1);
F=zeros(n,M+1);
for k=1:M+1
F(:,k)=X'.^(k-1);
end
A=F'*F;
B=F'*Y';
C=A\B;
C=flipud(C);


3. The attempt at a solution

These are the coefficients:
-0.0458x^3
0.5225x^2
-2.1567x
3.9040

I am confused with what the question is asking i know im suppose to have a ans for part A and B
Phys.Org News Partner Science news on Phys.org
NASA team lays plans to observe new worlds
IHEP in China has ambitions for Higgs factory
Spinach could lead to alternative energy more powerful than Popeye
Nok1
#2
Nov10-08, 12:29 AM
P: 18
Think about what a change of variable is, then figure out how to apply that to the data.

Aka, when you make a substitution for y=ln(y), that just means you take your y list, and just take the ln of that. That now because the new measurement for what used to be the y-axis.

Does that make sense?


Register to reply

Related Discussions
MATLAB Curve Fitting Question? Introductory Physics Homework 1
Curve-to-curve fitting trouble! Programming & Computer Science 5
Curve fitting in Matlab Math & Science Software 1
Curve fitting using Matlab Math & Science Software 0
Curve Fitting Calculus 4