# INF, NAN, and Null

These are special values that Analytica returns in special conditions:

**Inf**means infinity -- e.g., 1/0 -- or a real number larger than can be represented -- e.g. 1E307 * 100, because the maximum number it can handle is 1.796E308.**-Inf**rmeans negative infinity -- e.g., -1/0 -- or a number smaller than can be represented**NAN**means "Not A Number", where the result is numeric, but not a real number or infinity -- e.g., Sqrt(-1) or 0/0**Null**means that there is no such value. Slice, Subscript, SubIndex, or MdTable return Null, for example, when trying to Slice out the nth slice over an Index with less than n values.

### Computations with special values

Analytica follows ANSI (Association of National Standards Institutes) standards for computing with these special values, where applicable.

- 1/Inf → 0
- 1/(-Inf) → 0
- Inf + Inf → Inf
- Inf - Inf → NAN

When NULL appears in scalar operations, it generally produces a warning and evaluates to NULL, for example:

- 10 + NULL → NULL
- NULL - 10 → NULL
- 1 AND NULL → NULL

When NULL appears in an array operation, the result should be ignored. The common array reduction functions in Analytica 4.1 tend to support this as of release 4.1, but not prior to that, and not all array function support this. These examples demonstrate (assume A is indexed by I as indicated).

I: 1 2 3 4 5 A: 8 NULL 4 NULL 0

In Analytica 4.1, these array functions ignore Null: Sum, Min, Max, ArgMin, ArgMax, Product, Average, JoinText, Irr, Npv. Also Regression ignores data points which have Y=Null.

Array functions Sum, Min and Max also accept an optional parameter *IgnoreNaN* to ignore NaN values (otherwise they tend to be propagated).

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