Missing Values and Graphs
overview 

Missing Graph Values

In most cases, missing graph variables are ignored. Here are some special circumstances:

·    With time series plots, Minitab skips each interval that has a missing value, and connect lines do not extend across the missing category. Instead they stop at the previous nonmissing data value and begin again at the next data value.

·    With area graphs, if data are missing, the row must be missing in all series columns. Otherwise, Minitab cannot create an area graph.

·    With character graphs, if you use a column that contains missing values as an argument for a subcommand, Minitab generates an error message and does not produce a graph until you supply a valid subcommand and argument.

·    You can choose to include/not include empty cells on your graph. Empty cells are groups that only have missing values. These empty cell groups may occur with highly nested designs and may make the graph look cluttered.

 

For example, in this graph, the following groups are empty cells:

·    Ran1-Smokes1-Sex1-Activity0

·    Ran1-Smokes1-Sex2-Activity0, 1, and 3

·    Ran1-Smokes2-Sex1-Activity0

·    Ran1-Smokes2-Sex2-Activity0, 1, and 3

·    Ran2-Smokes1-Sex1-Activity1

·    Ran2-Smokes1-Sex2-Activity0

·    Ran2-Smokes2-Sex1-Activity0

·    Ran2-Smokes2-Sex2-Activity0

If you choose to not include empty cells, these groups would not appear on the graph.

For more information, see Include empty cells- Group Options.

Missing Categorical Values

In almost all graphs, you can choose to include/not include missing categorical values as a separate group in your graph.

 

For example, this is a boxplot of student pulse rates grouped by sex, when Sex contains a few missing values.

For more information, see Include missing as a group - Group Options.

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