Setting Options for the History Node

Selected fields. Using the Field Chooser (button to the right of the text box), select the fields for which you want a history. Each selected field is used to create new fields for all records in the dataset.

Offset. Specify the latest record prior to the current record from which you want to extract historical field values. For example, if Offset is set to 3, as each record passes through this node, the field values for the third record previous will be included in the current record. Use the Span settings to specify how far back records will be extracted from. Use the arrows to adjust the offset value.

Span. Specify how many prior records from which you want to extract values. For example, if Offset is set to 3 and Span is set to 5, each record that passes through the node will have five fields added to it for each field specified in the Selected Fields list. This means that when the node is processing record 10, fields will be added from record 7 through record 3. Use the arrows to adjust the span value.

Where history is unavailable. Select one of the following options for handling records that have no history values. This usually refers to the first several records at the top of the dataset, for which there are no previous records to use as a history.

• Discard records. Select to discard records where no history value is available for the field selected.
• Leave history undefined. Select to keep records where no history value is available. The history field will be filled with an undefined value, displayed as $null$.
• Fill values with. Specify a value or string to be used for records where no history value is available. The default replacement value is undef, the system null. Null values are displayed using the string $null$.

When selecting a replacement value, keep in mind the following rules in order for proper execution to occur:

• Selected fields should be of the same storage type.
• If all of the selected fields have numeric storage, the replacement value must be parsed as an integer.
• If all of the selected fields have real storage, the replacement value must be parsed as a real.
• If all of the selected fields have symbolic storage, the replacement value must be parsed as a string.
• If all of the selected fields have date/time storage, the replacement value must be parsed as a date/time field.

If any of the above conditions are not met, you will receive an error when executing the History node.