How can I call my function myfourier again with inputs specified and not entered from the user?

Question

Stefanos 2022-12-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1877667-how-can-i-call-my-function-myfourier-again-with-inputs-specified-and-not-entered-from-the-user

评论： Image Analyst 2022-12-14

%Q1

f = input('Please enter function rules for variable segments of the function f:')

flim= input('Please enter real numbers to define the limits of the segments of f:')

N= input('Please enter an intiger to specifie the max order of Fourier coefficients of f:')

function [a0 an bn fs] = myfourier(f, flim, N)

syms t

syms N

T = flim(end)-flim(1);

w0 = 2*pi/T;

fs = 0.0;

for i = 0:N

for k= 2:length(flim)

an= (2/T)*int(f(k-1)*cos(i*w0*t),t,flim(k-1),flim(k));

ann(i+1)=an;

bn= (2/T)*int(f(k-1)*sin(i*w0*t),t,flim(k-1),flim(k));

bnn(i+1)=bn;

fs= fs + an*cos(w0*i*t)+bn*sin(w0*i*t);

end

if i==0

fs = fs/2;

end

%a0 is calculated first (for i=0). The Fourier series starts with a0/2 ...

end

for k= 2:length(flim)

a0= (2/T)*int(f(k-1),t,flim(k-1),flim(k));

disp('a0=')

disp(a0)

end

for i= 1:N

disp('an=')

disp(ann(i+1))

end

for i= 1:N

disp('bn=')

disp(bnn(i+1))

end

fs

title("Fourier series approximation of f against estimated function f with N="+N)

hold on

fourier = matlabFunction(fs);

grid on

ax = gca;

ax.XAxisLocation = 'origin';

ax.YAxisLocation = 'origin';

xlabel('x')

ylabel('y')

t = flim(1):0.01:flim(end);

plot(t,fourier(t))

for k= 2:length(flim)

fplot(f(k-1),[flim(k-1), flim(k)])

end

legend('Fourier approximation of f')

end

%Q2

f= [-t- 2*pi, -t, 2*pi- t, -t-4*pi];

flim= [-3*pi,-pi,pi,3*pi,5*pi];

N= 5;

[a0 an bn fs] = myfourier(f, flim, N);

3 个评论
显示 1更早的评论隐藏 1更早的评论

Torsten 2022-12-14

编辑：Torsten 2022-12-14

在 MATLAB Online 中打开

Why don't you sum the an and bn to arrive at ann and bnn ? You just set ann(i+1) and bnn(i+1) to the integral over the last interval [flim(end-1):flim(end)], not over the complete interval [flim(1):flim(end)].

Why don't you divide ann(1) by 2 in the if-statement for the case i=0 ?

for i = 0:N
    for k= 2:length(flim)
        an= (2/T)*int(f(k-1)*cos(i*w0*t),t,flim(k-1),flim(k));
        ann(i+1)=an;
        bn= (2/T)*int(f(k-1)*sin(i*w0*t),t,flim(k-1),flim(k));
        bnn(i+1)=bn;
        fs= fs + an*cos(w0*i*t)+bn*sin(w0*i*t);
    end
    if i==0 
        fs = fs/2;
    end
    %a0 is calculated first (for i=0). The Fourier series starts with a0/2 ...
end

Why do you repeat the calculation of a0 that has already been done in the loop before for i=0 ?

for k= 2:length(flim)
    a0= (2/T)*int(f(k-1),t,flim(k-1),flim(k)); 
    disp('a0=')
    disp(a0)   
end

Image Analyst 2022-12-14

Original (I think) question below (for when he deletes it like he did for his other questions).

%Q1

f = input('Please enter function rules for variable segments of the function f:')

flim= input('Please enter real numbers to define the limits of the segments of f:')

N= input('Please enter an intiger to specifie the max order of Fourier coefficients of f:')

function [a0 an bn fs] = myfourier(f, flim, N)

syms t

syms N

T = flim(end)-flim(1);

w0 = 2*pi/T;

fs = 0.0;

for i = 0:N

for k= 2:length(flim)

an= (2/T)*int(f(k-1)*cos(i*w0*t),t,flim(k-1),flim(k));

ann(i+1)=an;

bn= (2/T)*int(f(k-1)*sin(i*w0*t),t,flim(k-1),flim(k));

bnn(i+1)=bn;

fs= fs + an*cos(w0*i*t)+bn*sin(w0*i*t);

end

if i==0

fs = fs/2;

end

%a0 is calculated first (for i=0). The Fourier series starts with a0/2 ...

end

for k= 2:length(flim)

a0= (2/T)*int(f(k-1),t,flim(k-1),flim(k));

disp('a0=')

disp(a0)

end

for i= 1:N

disp('an=')

disp(ann(i+1))

end

for i= 1:N

disp('bn=')

disp(bnn(i+1))

end

fs

title("Fourier series approximation of f against estimated function f with N="+N)

hold on

fourier = matlabFunction(fs);

grid on

ax = gca;

ax.XAxisLocation = 'origin';

ax.YAxisLocation = 'origin';

xlabel('x')

ylabel('y')

t = flim(1):0.01:flim(end);

plot(t,fourier(t))

for k= 2:length(flim)

fplot(f(k-1),[flim(k-1), flim(k)])

end

legend('Fourier approximation of f')

end

%Q2

f= [-t- 2*pi, -t, 2*pi- t, -t-4*pi];

flim= [-3*pi,-pi,pi,3*pi,5*pi];

N= 5;

[a0 an bn fs] = myfourier(f, flim, N);

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Askic V 2022-12-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1877667-how-can-i-call-my-function-myfourier-again-with-inputs-specified-and-not-entered-from-the-user#answer_1127437

在 MATLAB Online 中打开

If I understood your question correctly, sometimes you want to call a function when user needs to enter inputs, and sometimes you want to call same function with specified inputs.

In that case, you should write a function with with variable number of input arguments.

Just look this small example:

res1 = my_add()
res2 = my_add(3, 4)
function c = my_add(varargin)
    if nargin == 2
        a = varargin{1};
        b = varargin{2};
    else
        a = input('Enter first number: ');
        b =  input('Enter second number: ');
    end
    c = a + b; % or any other processing
end

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Stefanos 2022-12-14

This is what I want to do. Ask the user to enter inputs and then call again the function with inputs f, flim and N the ones shown in the description. Can you provide more explenations please?

请先登录，再进行评论。