error using fzero in a loop

I'm trying to find all the points between 0 and 10 where the derivative of y=0 by using (x1(H)+x2(H))/2) as a staring point but I keep on getting this error... Please help :(

Error using fzero (line 169) If FUN is a MATLAB object, it must have an feval method.

h=10;

ti=(1/200);

n=[1.2 2.9];

ni=[1 3];

na=[2 1];

x=[];

for k=1:numel(n)

x=sort([x (((0:1:1+(ceil(h/(n(k)))))-0.5)*(n(k)))]);

end

x1=(x(1:numel(x)-1));

x2=(x(2:numel(x)));

for T=[1:10];

nwa=[na.*sin((T*ti)*(pi./(ni)))];

for H=(1:numel(x1))

syms d;

y=sum(nwa.*cos(d.*(pi./n)));

X(H)=fzero(diff(y),(x1(H)+x2(H))/2);

end

P=(X(X>x1<x2))';

end

Answer 1

[dpb]

From the doc's for fzero

X = fzero(FUN,X0) ... FUN is a function handle.

Your code is

X(H)=fzero(diff(y),(x1(H)+x2(H))/2);

where you've entered an actual function.

[Tristan]

I can't figure out how to apply that though...

[dpb]

Well, it's not clear to me what your function is intended to be solving but the basic idea is to write a function either as an anonymous function or give the handle to an existing function and an initial guess and the fzero will find the value that provides a zero to that function on the assumption a zero-crossing can be found near (for some definition of near) x0.

Clarify what it is you're trying to get fzero to do for you here...

[Tristan]

I'm trying to find a way to calculate the position of the antinodes (the maximas and minimas) of a waveworm=sum(nwa.*cos(d.*(pi./n))) by using its derivative, and then using fzero starting at all the midpoints between consecutive multiples of n between 0 and 10.

[dpb]

There's an example in the doc on fzero using trig functions for formulation that should be illustrative.