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

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)

[Yusuf Selim KARATAS]

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.

Answer 1

[Image Analyst]

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