'mtimes' error and how to fix it

I am writing code and this error keeps popping up and I am not sure how to fix it:

deltap=2000;
mublood=.004;
L=30;
R=.005;
Rc=0:.0001:.005;
zi=Rc/R;
F=@(zi)1-16/7*sqrt(zi)+4/3*zi-1/21*zi.^4;
Q=((pi*R^4*deltap)/(8*(mublood)*L))*F;
plot(Q,Rc);
xlabel('Flow Rate');
ylabel('Changing R');

When I hit run it pops up with this error:

DRAFTFOR4_3
Undefined function 'mtimes' for input arguments of type 'function_handle'.

Error in DRAFTFOR4_3 (line 8)
Q=((pi*R^4*deltap)/(8*(mublood)*L))*F;

How do I fix it? Thanks

Answer 1

[Honglei Chen]

Your F function requires an input, so you need to call it with an input, such as

F(3)

[Walter Roberson]

Or F(zi)