Create function that functionally same to polyfit
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Create a user-defined function 'fitpoly' that has the same function as 'polyfit'
Reads the given data points from a text or Excel file and approximates the curve with an nth-order polynomial function
Set the input and output factors the same as ‘polyfit’
回答 (3 件)
Image Analyst 2022 年 5 月 17 日
There is still another way @종석 박 can do the assignment without plagiarizing. He can construct the equation like
Ax = y
using a for loop where A =
x(1)^n, x(1)^(n-1), x(1)^(n-2), ....., x(1), 1
x(2)^n, x(2)^(n-1), x(2)^(n-2), ....., x(2), 1
x(3)^n, x(3)^(n-1), x(3)^(n-2), ....., x(3), 1
x(m)^n, x(m)^(n-1), x(m)^(n-2), ....., x(m), 1
Then once you have the tall array you can do
coefficients = A \ y(:)
which is basically the method for doing least squares regression "manually".
Sam Chak 2022 年 5 月 16 日
I find it a little strange. Should your Intructor/Professor send you to learn the essentials through MATLAB Onramp at the beginning of the course in MATLAB?
From your description, it seems that your Intructor/Professor wants you to study the algorithm in polyfit.m.
This example only has 3 points, (1, 4), (2, 7), (3, 14). Try to improvise from here.
% Formulate the problem as a linear equation, A*x = b
P = [1 4; 2 7; 3 14]
x = P(:, 1)
A = [x.^2 x repelem(1, 3, 1)]
b = P(:, 2)
x = A\b