not enough input argument

This is my codes.

function [V] = TV(Dtank,Dpipe,Htank,Hwater)
h = Htank - Dtank/2; 
r = Dpipe/2;
pv = pi*r^2*h; 
ht = Hwater - h;
rt = Dtank/2;
wt = pi*(ht^2)*rt - (pi/3)*(ht^3);
V = pv + wt;
end

I am getting not enough input at line 2 but not sure what I am missing

[Rik]

How are you calling this function?

[Walter Roberson]

You cannot run that function just by clicking the green "run" button. You need to go to the command line and invoke it, passing in parameters. Or call it from another function that provides the arguments.