# Missing values

FastStats handles Missing values in the context of expressions and operators.

## IsMissing

Determines whether a value is Missing, returning true or false.

Expression

```apteco
IsMissing([Numeric Field])
```

For example, `If(IsMissing([Cost]),"No Value Present","Value Present")`.

When displayed on a Data Grid if an entry is missing output the words No Value Present if a value is present output the words Value Present.

## MissingValue

Returns a missing numeric value for specified entries.

Expression

```apteco
MissingValue()
```

For example, `If([Number of Bookings]<=0,MissingValue(), Value of Booking/Number of Bookings)`.

When displayed on a Data Grid output a blank for those entries with no bookings and an average per booking figure for those entries with 1 or more bookings.

## NotMissing

Determines whether a value is not missing, returning true or false.

Expression

```apteco
NotMissing([Numeric Field])
```

For example, `If(NotMissing([Value of Booking]),Value of Booking, 100)`.

When displayed on a Data Grid if a value is present (i.e. not missing) then output that value otherwise output the figure 100

## Reference missing values

Expressions that reference Missing values are evaluated as follows:

| Expression | Result |
| --- | --- |
| Missing + Missing | Missing |
| Value + Missing | Value |
| Missing - Missing | Missing |
| Value - Missing | Value |
| Missing - Value | \-Value |
| Missing \\\* Value | Missing |
| Missing / Value | Missing |
| Value / Missing | Missing |
| Missing / 0 | Missing |
| Missing % Value | Missing |
| Value % Missing | Missing |
| Missing % 0 | Missing |
| Missing ^ Value | Missing |
| Value ^ Missing | Missing |
| Value ^ Missing | Missing |
| Value \> Missing | true |
| Missing \> Value | false |
| Missing \> Missing | false |
| Value \\\< Missing | true |
| Missing \\\< Value | false |
| Missing \\\< Missing | false |
| Value \>= Missing | true |
| Missing \>= Value | false |
| Missing \>= Missing | false |
| Value \\\<= Missing | true |
| Missing \\\<= Value | false |
| Missing \\\<= Missing | false |
| Value = Missing | false |
| Missing = Missing | false |
| Value \<\> Missing | true |
| Missing \<\> Missing | false |
| Function(Missing) | All single parameter functions except IsMissing() evaluate to Missing |