What you should do is to make a small modification of your ODE-function - such that it takes an additional input argument where you can store all additional parameters that it needs. In this case a simple array will do the trick. Then you only need to collect these parameters in the script, and modify the ode45-call.
%% Script:
cylD=str2num(input('Cylinder Diameter (m)\n', 's'));
holeD=str2num(input('Hole Diameter (m)\n', 's'));
h0=str2num(input('Initial Height of Water\n', 's'));
tf=str2num(input('Time of Leak\n', 's'));
g = 9.81
A = pi*(cylD/2)^2
hole = pi*(holeD/2)^2
extraPars = [hole A g]; % Here we put the extra-parameters away, including
% g so we can use this on the moon etc
tspan=0:.05:tf
[t,h0]=ode45(@(t,h) TankIn(t,h,extraPars),tspan,h0); % here we create an
% "anonymous function" that
% ony depends on t and
% h, that uses the
% current value of
% extraPars in TankIn
plot(t,h0)
title('Height of Water vs Time Cylindrical Tank')
xlabel('time (s)')
ylabel('height (m)')
%% Function:
function dh = TankIn(t,h0,extraPars) % here we have the extraPars as a 3rd input
holeD = extraPars(1); % then we only need to extract these parameters
A = extraPars(2); % into the variables. I prefer to do it this way to keep
g = extraPars(3); % different steps separate.
k = holeD/A*sqrt(2*g);
dh = -k*sqrt(h0);
end
In my opinion it is cleaner to have all extra parameters in one additional array if possible. That way you dont need to modify the function-call in the ode45-calls you only need to modify the assignement to extraPars when you modify the TankIn-function.
HTH
