Error using feval Function to evaluate must be represented as a string scalar, character vector, or function_handle object.

my code is:

function vib = explicitwave(a,b,h,k,fic,gic,tm)

x = a:h:b;

nt = ceil(tm/k);

nx = ceil((b-a)/h);

nxm1 = nx - 1;

r = k/h;

r2 = r*r;

uinitial = feval(fic,x(2:nx));

u0 = [0 uinitial 0]';

u1(1) = 0

g = feval(gic,x);

for i = 2:nxm1

u1(i) = r/2*u0(i-1) + (1-r2)*u0(i) + r2/2*u0(i+1) - k*g(i);

end

u1(nx+1) = 0

vib = [u0 u1'];

Uoldest = u0;

Uold = u1';

for j = 3:nt

Unew(1) = 0;

for i = 2:nx

Unew(i) = r2*Uold(i-1) + 2*(1-r2)*Uold(i) + r2*Uold(i+1) - Uoldest(i);

end

Unew(nx+1) = 0;

vib = [vib Unew'];

Uoldest = Uold;

Uold = Unew;

end

time = 0:k:tmax;

titlestr = ['Wave Mesh Plot, times 0:tfinal = ' num2str(tm) ', step k = ' num2str(k)];

mesh(time, x, vib); title(titlestr); xlabel('Time'); ylabel('Position'); zlabel('Wave Values'); shg

end

my initial condition mfiles are:

gic.m

function initial = fic(x)

initial = 2*sin(pi*x);

end

and

fic.m

function initial = gic(x)

initial = -sin(2*pi*x);

end

Then I set a=0, b=1, tm=1, h=0.1, k=0.1, x = a:h:b, fic=fic(x), gic=gic(x)

Then when I try to run

explicitwave(a,b,h,k,fic,gic,tm)

I get the error:

Error using feval

Function to evaluate must be represented as a string

scalar, character vector, or function_handle object.

Error in explicitwave (line 10)

uinitial = feval(fic,x);

Can someone help me fix this problem?

Answer 1

[Sindhu Karri]

Hii,

Here the error is because of the feval function.You need to pass a function handle or function name as an input to feval .

Call the function as

explicitwave(a,b,h,k,@fic,@gic,tm)

without assigning fic=fic(x) and gic=gic(x).

And also tmax variable is not defined in the attached code

Refer to below link more understanding on feval function

feval