Microsoft Office Tutorials and References

In Depth Information

**Solving Recursive Equations**

Sometimes, this technique doesnâ€™t work. For example, the formula allows the possibility of a

division-by-zero error. The solution is to check for an error. If the formula displays an error, modify

the iterated value slightly. For example, the preceding formula can be rewritten using the

IFERROR function:

=IFERROR(1/(A1+1),A1+0.01)

IFERROR works only with Excel 2007 and later. The following version of the formula is

compatible with previous versions of Excel:

=IF(ISERR(1/(A1+1)),A1+0.01,1/(A1+1))

Figure 129-2 shows a worksheet that calculates several recursive equations in column B. The

formulas in column D provide a check of the results. For example, the formula in column D2 is

=1/(B2+1)

Formulas in column E display the difference between the values in column B and column D. If the

solution is correct, column E displays a zero (or a value very close to zero).

Figure 129-2:
This workbook uses circular references to calculate several recursive equations.