matlab切比雪夫拟合

function [ res ] = ChebyShev(num,i)

if i==0 
    res=1;
elseif i==1
    res=num;
else
    res=2*num*ChebyShev(num,i-1)-ChebyShev(num,i-2);
end
   
end

function [ coeff ] = ChebyCoeff( xfile,timefile )

x=load(xfile);
time=load(timefile);
B=zeros(length(time),11); %B
L=x;%L
sec_start=time(1);
sec_end=time(end);
for i=1:length(time)
     chang_sec=(2*time(i)-(sec_start+sec_end))/(sec_end-sec_start);
    for j=1:11
        B(i,j)=ChebyShev(chang_sec,j);
    end
end
coeff=(B‘*B)\(B‘*L);
end

function [ res ] = ChebyValue( timefile,coeff,num )

res=0;
time=load(timefile);
change_time=(2*num-(time(1)+time(end)))/(time(end)-time(1));
for i=1:length(coeff)
    res=res+coeff(i)*ChebyShev(change_time,i);
end

end