Problem during the use of 'fzero'

During the exxecution of my codes, the compiler returns this error which I can't understand completely ... Some help ?

Error:

Error using fzero>localFirstFcnEval

FZERO cannot continue because user-supplied

function_handle ==> f failed with the error below.

Not enough input arguments.

Error in fzero (line 305)

fx = localFirstFcnEval(FunFcn,FunFcnIn,x,varargin{:});

Error in AnalisiVibrazioniAuto (line 19)

point = fzero(fun,x0);

Here below the code:

clc
clear
close all
%% Global variables declaration
global c
c = 1.4*10e4;
global m 
m = 1.2*10e3;
global k 
k = 1.25*10e6;
%% Initial condition
x0 = 0.3;
%% Physical parameters
n = c/(2*m);
p = sqrt(k/m-(c^2)/(4*m^2));
%% Function to examinate
t = 0:0.1:1;
fun = @f;
point = fzero(fun,x0);
%figure
%plot(t,fun,'r');
%plot(t,point,'g');
%hold on

-------------------------------------

function fun = f(x,n,p,x0)
fun = (exp(-n.*x)).*((x0.*cos(p.*x))+(x0.*n/p.*sin(p.*x)));
end

Thanks :)

Answer 1

[Star Strider]

I am not certain what you want to do.

I suspect that you want to loop over varying values of ‘t’ however ‘t’ never appears as an argument to ‘f’ or as far as I can determine, an other calculation.

The ‘f’ funciton has to have all its arguments supplied, even if you are only solving for one of them.

This illustrates that reference —

%% Global variables declaration
% global c
c = 1.4*10e4;
% global m 
m = 1.2*10e3;
% global k 
k = 1.25*10e6;
%% Initial condition
x0 = 0.3;
%% Physical parameters
n = c/(2*m);
p = sqrt(k/m-(c^2)/(4*m^2));
%% Function to examinate
t = 0:0.1:1;
fun = @(x)f(x,n,p,x0);
point = fzero(fun,x0)

point = 0.2531

%figure
%plot(t,fun,'r');
%plot(t,point,'g');
%hold on
% -------------------------------------
function fun = f(x,n,p,x0)
    fun = (exp(-n.*x)).*((x0.*cos(p.*x))+(x0.*n/p.*sin(p.*x)));
end

Also, using global variables is considered to be bad programmiung practice. They are not used anywhere here, anyway. Instead, pass them as arguments as appropriate.

.

[Andrea Quintavalle]

Thanks. Now is all clear

[Star Strider]

My pleasure!

Answer 2

[Torsten]

I'm surprised the initial value x0 is part of your function definition. Are you sure this is correct ?

%% Global variables declaration
global c
c = 1.4*10e4;
global m 
m = 1.2*10e3;
global k 
k = 1.25*10e6;
%% Initial condition
x0 = 0.3;
%% Physical parameters
n = c/(2*m);
p = sqrt(k/m-(c^2)/(4*m^2));
%% Function to examinate
t = 0:0.01:1;
fun = @(x)f(x,n,p,x0);
point = fzero(fun,x0);
hold on
plot(t,fun(t),'r');
plot(point,fun(point),'o');
hold off
grid on

%-------------------------------------
function fun = f(x,n,p,x0)
fun = (exp(-n.*x)).*((x0.*cos(p.*x))+(x0.*n/p.*sin(p.*x)));
end

[Andrea Quintavalle]

I'm a bit surprised too ... Tomorrow I'll check the answer at lesson