Chart - ValueAxis.major/minor_unit

The value axis has major and minor divisions, corresponding to where tick marks, tick labels, and gridlines appear, when present. How frequently these appear is determined by the major/minor units setting, specified as a floating point number of units to skip between divisions. These settings may be specified explictly, or PowerPoint can determine a sensible default based on the chart data. The latter setting is labeled ‘Auto’ in the UI. By default, major and minor unit are both set to ‘Auto’ on new charts.

Candidate protocol

The properties ValueAxis.major_unit and ValueAxis.minor_unit are used to access and change this setting.

None is used as an out-of-band value to signify Auto behavior. No separate boolean properties are required.

>>> value_axis = chart.value_axis
>>> value_axis.major_unit
None
>>> value_axis.major_unit = 10
>>> value_axis.major_unit
10.0
>>> value_axis.major_unit = -4.2
Traceback ...
ValueError: must be positive numeric value
>>> value_axis.major_unit = None
>>> value_axis.major_unit
None

Microsoft API

Axis.MajorUnit
Returns or sets the major units for the value axis. Read/write Double.
Axis.MinorUnit
Returns or sets the minor units on the value axis. Read/write Double.
Axis.MajorUnitIsAuto
True if PowerPoint calculates the major units for the value axis. Read/write Boolean.
Axis.MinorUnitIsAuto
True if PowerPoint calculates minor units for the value axis. Read/write Boolean.

PowerPoint behavior

Major and minor unit values are viewed and changed using the Scale pane of the Format Axis dialog. Checkboxes are used to set a value to Auto. Changing the floating point value causes the Auto checkbox to turn off.

XML Semantics

  • Only a value axis axis or date axis can have a <c:majorUnit> or a <c:minorUnit> element.
  • Auto behavior is signified by having no element for that unit.

XML specimens

Example value axis XML having an override for major unit:

<c:valAx>
  <c:axId val="-2101345848"/>
  <c:scaling>
    <c:orientation val="minMax"/>
  </c:scaling>
  <c:delete val="0"/>
  <c:axPos val="l"/>
  <c:majorGridlines/>
  <c:numFmt formatCode="General" sourceLinked="1"/>
  <c:majorTickMark val="out"/>
  <c:minorTickMark val="none"/>
  <c:tickLblPos val="nextTo"/>
  <c:crossAx val="-2030568888"/>
  <c:crosses val="autoZero"/>
  <c:crossBetween val="between"/>
  <c:majorUnit val="20.0"/>
</c:valAx>