perlchartdir.StartOfMonthFilter

Creates a data filter that matches date/times that represent the start of a new month in a date/time series.

This method is typically used in Axis.setMultiFormat and Axis.setMultiFormat2 to select specific dates/times for formatting as axis labels.

In a date/time series, an element is considered that start of a new month if it is of a different month than the previous element. It does not need to be at exactly the starting instance of the month.

For the first element of the date/time series, because there is no previous element to compare with, it will be considered as the start of a new month if it is "near" the exact starting instance of the current month, in which "near" is defined using the initialMargin argument, expressed as a ratio (0 to 1) of the month duration.

Argument	Default	Description
labelStep	1	For dates/times that matches the start of month criteria, picks only 1 out of every "labelStep" number of elements. For example, if this argument is 3, only 1 of every 3 elements that at at the start of month will be selected.
initialMargin	0.05	If the first label is "near" the exact starting instance of the current month to within the ratio specified in the initial margin, it will be considered to have matched the start of month criteria.