Time scale for control charts

This topic is about the time scale on a control chart, such as the x-axis on an Xbar chart. For information on other scale types, click one of the following links.

Show or hide scale elements

Graph scale elements are axis lines, axis labels, tick marks, and tick labels. You can display these elements on the high side or the low side of the graph's data region.

For example, on the following time series plot, the continuous (y) scale displays tick labels with tick marks on the low side. The time (x) scale displays tick labels with tick marks on the low side. Axis lines are on all sides.

To specify which elements to include when you create a graph, click Scale, then select the elements on the Axes and Ticks tab. To change or add the elements on an existing graph, double-click the scale, then select the elements on the Show tab.

Specify the time scale labels

To specify the labels to use when you create a control chart, click Scale, then specify the labels on the Time tab. To change or add the labels on an existing graph, double-click the x-scale, then specify the labels on the Time tab.

Index
Label the x-axis with the number of the subgroup.
Stamp
Label the x-axis with values from a column. In Stamp columns (1-3, innermost first), enter up to three columns that contain date/time, numeric, or text values for the scale.

Change the position of the tick marks

When you create a graph, Minitab sets the tick mark positions to fit the time scale. To change the tick mark positions, double-click the scale. On the Scale tab, under Tick Positions, specify one of the following:
Automatic
Display the tick marks in their default positions.
Specify tick positions
Enter the tick position numbers at which you want tick marks to appear. You can enter a series of numbers or specify a range of values. Use a colon between two numbers to indicate the range. Use a slash after the range to indicate an increment amount. For example, 5:30/5 places tick marks at 5, 10, 15, 20, 25, and 30.
For example, on the time series plot with custom tick mark positions, the first tick mark on the time scale is at position 4 (April). The increment is 3 (every third month).
Default tick mark positions
Custom tick mark positions
Note

You can specify the time scale values and range on the Time tab.

Change the scale range

For a time scale, Minitab sets the scale range so that the observations extend the length of the axis. If you want to compress or expand the display of observations on the axis, double-click the time scale. On the Scale tab, under Scale Range, deselect Auto for Minimum or Maximum, then enter the new minimum or maximum.

Change the axis line attributes and tick orientation

To change the color, size, and line type of the axis lines and tick marks, and the orientation of tick marks and the length of major tick marks, double-click the scale, then specify the options on the Attributes tab. The following images illustrate the tick orientation.
Outside
Inside
Out and In

Change the tick mark labels

When you create a graph, Minitab uses data values as tick mark labels. To specify custom tick mark labels on an existing graph, double-click the scale. On the Labels tab, select Specified, then enter custom labels, separated by spaces.

For example, on the first graph, the default labels are rotated because they are too long to fit. The shorter custom labels on the second graph fit better.
Default tick mark labels
Custom tick mark labels

Edit the font for the tick mark labels on the Font tab. Change the angle of tick mark labels on the Alignment tab.

Change the axis labels

To edit an axis label, double-click the label. On the Font tab, edit the text, and the font. On the Alignment tab, specify the text angle and the position relative to the default location.

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