Apple iWork '09 - Manual (Page 257)

Chapter 10 Statistical Functions 257
“Value Types” on page 36
“The Elements of Formulas” on page 15
“Using the Keyboard and Mouse to Create and Edit Formulas” on page 26
“Pasting from Examples in Help” on page 41
FREQUENCY
The FREQUENCY function returns an array of how often data values occur within a
range of interval values.
FREQUENCY(data-values, interval-values)
 data-values: A collection containing the values to be evaluated. data-values is a
collection containing number or date/time values. All values should be of the same
type.
 interval-values: A collection containing the interval values. interval-values is a
collection containing number or date/time values. All values should be of the same
type as the values in the data-values collection.
Usage Notes
FREQUENCY determines the number of values in  data-values that fall within each
interval. The interval array is easiest to understand if it is arranged in ascending
order. The first frequency will be the count of those values that are less than or
equal to the lowest interval value. All other frequency values, except the last, will be
the count of those values that are greater than the immediately lower interval value
and less than or equal to the current interval value. The final frequency value will be
the count of those data values that are greater than the largest interval value.
The values returned by the function are contained in an array. One method of
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reading the values in the array is to use the INDEX function. You can wrap the
FREQUENCY function within the INDEX function: =INDEX(FREQUENCY(data-values,
interval-values), x) where x is the desired interval. Remember that there will be one
more interval than there are interval-values.