Setting variables to constants in MATLAB

I have a set of differential equations and I want to set some of the variables to be constant.

For instance,

dy1dt = f(..)

dy2/dt = g(..)

Here, want to set y2 to be constant always.

constant y2;

Is this the right to deifne y2 to be constant?

[Walter Roberson]

No, MATLAB does not have any "constant" statement.

[madhan ravi]

What do you mean by setting variables to constant?

[Torsten]

Set dy2/dt = 0. This makes y2 remain at its initial value.

[Deepa Maheshvare]

Thank you, everybody