Page 426 - Excel for Scientists and Engineers: Numerical Methods

APPENDIX 3 CUSTOM FUNCTIONS HELP FILE 403

Rungel
Performs fourth-order Runge-Kutta integration of an ordinary differential equation.
Returns the value of the independent variable y at x + Ax, based on specified values of x
and y at x, and a differential equation.

Syntax
Ru ngel (x- variable, y- variable, deriv-formula, interval)
x- varia ble the value of x
y-variable the value of y at x
deriv-formula the differentia I equation dyjdx = f (x- varia ble, y- varia ble)
interval Ax, the interval for the calculation

Remarks
The argument x-variable can be a value, or a reference to a cell containing a value
or a formula.
The argument y-variable can be a value, or a reference to a cell containing a value
or a formula.
The argument deriv-formula can be a value, or a reference to a cell containing a
value or a formula.
The argument interval can be a value or a formula, or a reference to a cell
containing a value or a formula.
The workbook can be set to either RlC1- or Al-style.

Limitations
None of the precedent cells of the argument expression may contain references to
the argument reference.
The function cannot handle implicit references; that is, a name or range reference
cannot be used for a range of values.

See Also
Runge, Runge3