index exceeds matrix dimension,Subscript indices must either be real positive integers or logicals

I am a total noob in matlab and i am trying to write a code for water hammer simulation in a series pipe system, and the error i am getting is index exceeds matrix dimension, apparently for this line of code v1(1,t+dt1)=((((-a1)^2)*v1(2,t+dt1))/(h1(2,t+dt1)-h1(1,t+dt1))*g-a1^2); and also i am getting the error of Subscript indices must either be real positive integers or logicals, for the code h1(1,t+dt1)=Zu; this are both inlet boundary conditions. Zu has been defined earlier with a value of 40.

would be grateful if anyone can guide me through this or point towards something that can help me.

[Andy]

With only this line of code to examine, all that I can say is that it looks like t or dt1 are combining to produce an invalid number. Without seeing the rest of the code it is impossible to say how. If I get this sort of error I normally insert a statement disp(t) or leave the ; off the end of the line that sets the variable causing it to show in the command window. That usually points me in the right direction for further investigation.

[KALYAN ACHARJYA]

Please share complete code, so that we can see the issue?

Answer 1

[KSSV]

v1(1,t+dt1)=((((-a1)^2)*v1(2,t+dt1))/(h1(2,t+dt1)-h1(1,t+dt1))*g-a1^2)

In the above I could say that dt1 is a fraction...and you are tryigng to index arrays with fractions/ negatives. Note that MATLAB accepts only posittive integers and logicals as index.

A = rand(10) ; 
A(1)   % allowed, no error 
A(10)  % allowed, no error 
A(1,2)  % allowed, no error 
A(-10)  % error, index cannot be negative
A(0)  % error, not allowed index cannot be zero unless it is logical.
A(1.25)  % not allowed

You need to re think on your code.