Chebyshev Polynomial functions of the first kind

Question

Katerina Polykarpou 2020-2-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/505537-chebyshev-polynomial-functions-of-the-first-kind

评论： Katerina Polykarpou 2020-2-14

function y = myChebyshevPoly1(n,x)
%y = myChebyshevPoly1(n,x)
%y is the vector for the first n Chebyshev numbers
if n == 0
    out = 1; %first base case
else if n == 1
        out = x; %second base case
    else 
        out = 2*x*myChebyshevPoly1((n-1),x)-myChebyshevPoly1((n-2),x);%recursive call
    end
end % end myChebyshevPoly1
>>x = myvec/26;
>> n = 5;
>> y = myChebyshevPoly1(n,x)

when i run it and apply the following commands it will appear as error can someone explain to me what am i doing wrong?

also how can i ensure that expression above works for the case when x is a vector.

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Answer 1

Patrick Gipper 2020-2-14

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https://ww2.mathworks.cn/matlabcentral/answers/505537-chebyshev-polynomial-functions-of-the-first-kind#answer_415613

在 MATLAB Online 中打开

You just need to replace "out" with "y". Maybe you already caught this?

function y = myChebyshevPoly1(n,x)
%y = myChebyshevPoly1(n,x)
%y is the vector for the first n Chebyshev numbers
if n == 0
    y = 1; %first base case
else if n == 1
        y = x; %second base case
    else 
        y = 2*x*myChebyshevPoly1((n-1),x)-myChebyshevPoly1((n-2),x);%recursive call
    end
end % end myChebyshevPoly1

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Patrick Gipper 2020-2-14

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Oh right, I just used a scalar test case. One change fixes that.

function y = myChebyshevPoly1(n,x)
%y = myChebyshevPoly1(n,x)
%y is the vector for the first n Chebyshev numbers
if n == 0
    y = 1; %first base case
else if n == 1
        y = x; %second base case
    else 
        y = 2*x.*myChebyshevPoly1((n-1),x)-myChebyshevPoly1((n-2),x);%recursive call
    end
end % end myChebyshevPoly1