## Type and Solve ODE's

> Pick and drag new initial point in the viewer window. This modifies the initial `x` and `y` values. Initial values of higher derivative of `y` can be modified inside the text field `Initial y`.

> Type a new differential equation. Whenever you type in a text field press enter to submit your changes. Use keyboard key `i` to switch back to mode allowing picking of initial values:

> i | pick initial `x` and `y` values

> The integrator is a fourth-order Runge-Kutta method with constant step size.

> ### Controls in ODE project panel:

> ODE text field | Type a new ordinary differential equation. Higher derivatives of `y` must be denoted `dy, d2y` or `d3y`. In this text field you can use all mathematical functions shown in Expressions.html.
> Text field "Order" | Defines the order (highest derivative of `y`) of the differential equation
> Slider "Step Size" | Discretization for `x`-values
> Slider "Length" | Length of the `x`-interval to evaluate the differential equation.
> Slider "Initial x" | Minimum value for `x`-interval
> Text fields "Initial y" | The first text field shows the initial `y`-value, the second text field shows the initial value of the first derivative of `y`, if "Order" is greater than 2, further text fields for the higher derivatives are displayed.

> View source code:
> PaExprOde.java of applet,
> PjExprOde.java of project,
> PjExprOde_IP.java of project panel.