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Options for dealing with missing data in a graph

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You can control how missing values and empty cells are graphed, in the graph creation dialog box.

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About missing groups and empty cells

In the following worksheet, the two grouping variables Style and Size each have three values. However, some data are missing.

C1-T C2-T C3
Style Size Quantity
Short Small 4
Short Medium 6
Short Large 3
Long Small 3
Long Medium 7
Long Large 2
  Small 5
Hooded Small 1
Hooded Medium 4
Missing group
One row contains a missing value in the Style column with Small in the Size column. This set of data is considered a "missing group".
Empty cell
The group Hooded/Large does not appear here. This combination is considered an "empty cell". You can exclude empty cells to save space on your graph, or to show that the group does not exist.

Include missing group name data

By default, Minitab treats missing group names as a separate group. For example, rows 2 and 4 in the following worksheet contain missing values instead of A or B. The interval plot includes a separate group for these rows. (Because the group name is missing for these rows, the tick mark label is also missing.)
C1-T C2
Group Data
A 22
30
B 47
25
... ...
To exclude groups that have missing names when you create the graph, complete the following steps:
  1. Click Data Options.
  2. On the Group Options tab, deselect Include missing as a group.

Include empty data cells

By default, Minitab includes all possible groups on a graph, including groups that have no data. For example, the following bar chart includes a tick mark for group A2, but no bar. A2 is an empty cell because no worksheet rows contain an A in column C1 and a 2 in column C2.
C1-T C2 C3
Group Subgroup Data
A 1 55
B 1 41
B 2 29
C 1 44
C 2 33
To exclude empty cells when you create a graph, complete the following steps:
  1. Click Data Options.
  2. On the Group Options tab, deselect Include empty cells.
To remove empty cells from an existing graph, complete the following steps:
  1. Double-click the graph.
  2. Double-click the scale to open the Edit Scale dialog box.
  3. On the Scale tab, deselect Include empty cells.

Examples of including or excluding missing groups and empty cells

The following examples graph data from the previous worksheet to show all possible combinations.

Do not include missing as a group, do not include empty cells

If you deselect both Include missing as a group and Include empty cells, Minitab excludes the group Hooded/Large and the group created by a missing value and Small.

Include missing as a group, do not include empty cells

If you select only Include missing as a group, Minitab includes a bar for the "missing group" formed by an empty cell and the value Small.

Do not include missing as a group, include empty cells

If you select Include empty cells, Minitab includes an empty placeholder for the group Hooded/Large.

Include missing as a group, include empty cells

If you check both Include missing as a group and Include empty cells (the defaults), Minitab includes both empty cell and missing groups from the earlier examples, as well as the empty cells created by their combination (a missing value with "Medium" and a missing value with "Large"). When used in the context of paneling, these options have a similar effect on the number of panels.

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