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Extended data:
Matters needing attention
The function command is:
A=polyfit(x, y, m)% x, y is the corresponding independent variable, and m is the highest power to be fitted.
y=polyval(a,x); ? % According to the fitted function, the value of the dependent variable corresponding to x is obtained.
The expression of the function is f (x) = a1* xm+...+am * x+a _ m+1.
Polyfit(x, y, n), where: x, y are vectors of known data points, representing abscissa and ordinate respectively, and n is the degree of fitting polynomial, and the result returns fitting polynomial coefficients of m degrees, which are stored in vector p from high order to low order. Parameter p is a fitting polynomial y = A 1x n+...+ANX+A, totaling n+6550.
Example:
% polynomial fitting
x =(0:0. 1:7)';
y = sin(x);
P = polyfit(x, y, 3) %p is the polynomial coefficient after fitting.
z=polyval(p,x);
plot(x,y,' r ',x,z,' b ')
Where p is the polynomial coefficient after fitting, and the running result is:
p = 0.0736-0.7095 1.5250-0.0296