undefined function 'f'

Question

Titas Chattopadhyay 2020-3-31

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514195-undefined-function-f

评论： Ameer Hamza 2020-3-31

tmesh = linspace(0,pi/2,5);
solinit = bvpinit(tmesh, @f);
sol = bvp4c(@odefun, @bcfun, solinit);
 plot(sol.x, sol.y, '-o');
 

FUNCTION

function dzdt = odefun(t,z)
dzdt = zeros(2,1);  
dzdt = [z(2)+z(1)];    
end
% boundary conditions
function res = bcfun(za, zb)
    res = [za(1) zb(pi/2)-2]
end
% Initial guess
function g = f(t)
 g = [sin(t) cos(t)];
end

error unrecognized function or variable 'f'

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Walter Roberson 2020-3-31

If you stored those three functions together in one file, and had the script in another file, then the script would only be able to see the first function inside the file of functions. Only the first function in a file of functions is visible to the outside normally; the rest are private implementations only for use by that function (typically)

Titas Chattopadhyay 2020-3-31

So, I have to make 3 function files for func ,bcs and ics. Right?

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Answer 1

Ameer Hamza 2020-3-31

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514195-undefined-function-f#answer_423048

编辑：Ameer Hamza 2020-3-31

在 MATLAB Online 中打开

Either write all the functions in one file like this. (Also note that I have made few changes in your code.)

tmesh = linspace(0,pi/2,5);
solinit = bvpinit(tmesh, @f);
sol = bvp4c(@odefun, @bcfun, solinit);
plot(sol.x, sol.y, '-o');
function dzdt = odefun(t,z)
    dzdt = zeros(2,1);  
    dzdt = [z(2); z(1)]; % <----- This should be a 2x1 vector
end
% boundary conditions
function res = bcfun(za, zb)
    res = [za(1); zb(2)-2]; % <---- boundary conditions are written like this, zb(pi/2) is invalid
end
% Initial guess
function g = f(t)
    g = [sin(t) cos(t)];
end

Or create 4 files like this.

main_script:

tmesh = linspace(0,pi/2,5);
solinit = bvpinit(tmesh, @f);
sol = bvp4c(@odefun, @bcfun, solinit);
plot(sol.x, sol.y, '-o');

odefun.m:

function dzdt = odefun(t,z)
    dzdt = zeros(2,1);  
    dzdt = [z(2); z(1)];    
end

bcfun.m:

% boundary conditions
function res = bcfun(za, zb)
    res = [za(1); zb(2)-2];
end

f.m:

% Initial guess
function g = f(t)
    g = [sin(t) cos(t)];
end

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Titas Chattopadhyay 2020-3-31

Thank you so much.

Ameer Hamza 2020-3-31

Glad to be of help.

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undefined function 'f'

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