GCHART Procedure

Understanding Chart Variables

About Chart Variables

The chart variable is the variable in the input data set whose values determine the categories of data represented by the bars, blocks, slices, or spines. The chart variable generates the midpoints to which each observation in the data set contributes.

The chart variable can be either character or numeric. Character chart variables contain character values, which are always discrete. Numeric chart variables fall into two categories: discrete and continuous.

Note: You can apply a format that converts multiple values or a range of values to a single formatted value. In this case the GCHART procedure produces a single midpoint for that single formatted value.

Discrete variables contain a finite number of specific numeric values that are to be represented on the chart. For example, a variable that contains years, such as 1984 or 2001, is a discrete variable.
Continuous variables contain a range of numeric values that are to be represented on the chart. For example, a variable of temperature data that contains real values between 0 and 212 is a continuous variable.

Numeric chart variables are always treated as continuous variables unless the DISCRETE option is used in the action statement, or, unless a format is used to group ranges of values. In most cases it is a good idea to specify the DISCRETE option when using date values.

Missing Values

By default, the GCHART procedure ignores missing midpoint values for the chart variable. If you specify the MISSING option, then missing values are treated as a valid midpoint and are included on the chart. Missing values for the group and subgroup variables are always treated as valid groups and subgroups.

When the value of the variable that is specified in the FREQ= option is missing, 0, or negative, the observation is excluded from the calculation of the chart statistic.

When the value of the variable specified in the SUMVAR= option is missing, the observation is excluded from the calculation of the chart statistic.