MATLAB: Matlab give me error

argument

function hdot = height(t,h)

hdot = -(0.0334*sqrt(h))/(10*h-h^2);

[t, h] = ode45 (@height, [0 2475], 9);

plot(t,h),xlabel('Time (sec)'),ylabel('Height (ft)')

end

Best Answer

You need to move the ode45 and plot statements out of the function. Run it like this

[t, h] = ode45 (@height, [0 2475], 9);
plot(t,h)
xlabel('Time (sec)')
ylabel('Height (ft)')
function hdot = height(t,h)
    hdot = -(0.0334*sqrt(h))/(10*h-h^2);
end

Related Solutions

MATLAB: Not enough input arguments

How are you calling it? What value are you passing in for t? You're not just clicking the green run triangle without giving it a value for t are you? So, let's say t was 10. Are you doing

t = 10;
h = height(t); % Pass in t to the height() function.
fprintf('For t = %.1f, height = %f.\n', t, h);

So, what is your program for calling your height() function? Evidently from the error it thinks you're doing this:

h = height(); % Not passing in anything for t.  This will throw an error.

or else you're clicking the green run triangle which will try to run the function without sending in anything for t.

MATLAB: ODE Solver wont input P1 function

Since ‘rhs’ is a function nested inside ‘first_oder_ode’, it will inherit all the variables in the ‘first_oder_ode’ workspace. The reverse is not true, so you have to calculate ‘P1’ separately outside ‘rhs’ and after your ode45 call.

Your code with those changes:

function first_oder_ode 
 
% SOLVE  dx/dt = -3 exp(-t). 
% initial conditions: x(0) = 0 
CV1=110*0.1336806;
CV2=110*0.1336806;
Area=15; % cross sectional area of tank, m^2
P0=1.0*10^5;
P3=1.1*10^5;
rho=1000;
g=9.8;
k0=10.09782398;
kM=423463.7642;
ka=8.869925491;
k1=0.633075579;
k2=5.742728899;
t=0:0.001:10;   % time scalex 
initial_h=0; 
[t,h]=ode45( @(t,h) rhs(t,h) , t, initial_h); 
P1=k0+kM*(1+(ka-k1)/(k1-k2)*exp(-t/k1)+(ka-k2)./(k2-k1).*exp(-t/k2));
figure(1);
plot(t,h); 
xlabel('t'); ylabel('h'); 
figure(2);
plot(t,P1);
xlabel('t'); ylabel('P1');
    function dhdt=rhs(t,h) 
P1=k0+kM*(1+(ka-k1)/(k1-k2)*exp(-t/k1)+(ka-k2)/(k2-k1)*exp(-t/k2));
P2=P0+rho*g*h;
Qin=CV1*(P1-P2);
Qout=CV2*(P2-P3);
       dhdt = (Qout-Qin)/Area;
    end 
end

Then just call it from a script or your Command Window as:

first_oder_ode

to run it.

Best Answer

Related Solutions

MATLAB: Not enough input arguments

MATLAB: ODE Solver wont input P1 function

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