need help to fix the error! least square curve d = E *t^2 + D* t

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Ahmed
Ahmed 2020-12-1
回答： Image Analyst 2020-12-1
function [ m, Y ] = pnnnfit( x, y, n )
m=polyfit(x,y,n)
y_new=polyval(m,x)
er_sq=(y-y_new).^2
Y=sum(er_sq)
end
x=[0 0 0;1 1 0;4 2 0; 9 3 0; 16 4 0; 25 5 0; 36 6 0; 49 7 0; 64 8 0; 81 9 0; 100 10 0];
y=[ 0; -5.2;-8.10;-8.46;-6.38;-1.84;5.15;14.59;26.48;40.83;57.63];
pnnnfit(x,y,2)
Error using polyfit (line 44)
The first two inputs must have the same number of elements.
Error in pnnnfit(line 2)
t=polyfit(x,y,n)
  1 个评论
Yusuf Selim KARATAS
Yusuf Selim KARATAS 2020-12-1
Dear Ahmed,
I do not know which line is 44 but as far as I understand you have x matris [3x11] and y matris as [1x11]. Matlab warns you that these two need to have same dimensions.
I am not sure. I just wanted to give you an idea.
THanks.

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回答（1 个）

Image Analyst
Image Analyst 2020-12-1
x has 3 columns whereas y has only 1. Try fitting only one column of x, like this:
x=[0 0 0;1 1 0;4 2 0; 9 3 0; 16 4 0; 25 5 0; 36 6 0; 49 7 0; 64 8 0; 81 9 0; 100 10 0]
y=[ 0; -5.2;-8.10;-8.46;-6.38;-1.84;5.15;14.59;26.48;40.83;57.63]
% Fit first column only
[m, Y] = pnnnfit(x(:, 1), y, 2)
function [coefficients, MSE] = pnnnfit(x, y, order)
coefficients = polyfit(x, y, order)
y_fitted = polyval(coefficients, x)
squaredError = (y - y_fitted) .^ 2
MSE = sum(squaredError)
end

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