Question

matlab中出现Undefined function or variable 'X'.请高人帮忙分析下，谢谢

function C=ispoiy(X,Y,M)
%Input -X is the 1xn abscissa vector
% -Y is the 1xn ordinate vector
% -M is the degree of the least-squares polynomial
%Output-C is the coefficient list for the polynomial
n=length(X);
B=zeros(1:M+1);
F=zeros(n:M+1);
%Fill the columns of F with the powers of X
for k=1:M+1
F(:,k)=X'.^(K-1);
end
%Solve the linear system from(25)
A=F'*F;
B=F'*Y;
C=A\B;
C=flipud(C);
一直报错
C=ispoiy(X,Y,M)
??? Undefined function or variable 'X'.

Answer 1

函数本身存在错误，修改后，将下面函数保存为ispoiy.m。
function C=ispoiy(X,Y,M)
%Input -X is the 1xn abscissa vector
% -Y is the 1xn ordinate vector
% -M is the degree of the least-squares polynomial
%Output-C is the coefficient list for the polynomial
n=length(X);
B=zeros(1:M+1);
F=zeros(n:M+1);
%Fill the columns of F with the powers of X
for k=1:M+1
F(:,k)=X'.^(k-1)%为小k
end
%Solve the linear system from(25)
A=F'*F;
B=F'*Y';%Y为转置
C=A\B;
C=flipud(C);

然后对X,Y,M赋值。
例如：
在命令窗口输入：
X=[1 2 3 4];Y=[4 5 6 7];M=length(X)-1;%要求X，Y维数一致，
C=ispoiy(X,Y,M)

Answer 2

X没有赋值