Like its cousin, the standard Row Filter, the Rule-based Row Filter is used to dynamically remove records from a table. However, unlike the Row Filter, the Rule-based Row Filter allows you to create multiple logical expressions to fine-tune your filtering.
The cofiguration menu displays these panes:
- Column List: A list of all column names in the table
- Flow Variable List: A list of all flow variables attached in the stream
- Functions: A list of logical functions and operators available
- Description: A written explanation of what a selected function does and how to use it
- Expression: Where you will enter the filter expression
Writing Expressions
At first, writing expressions in the Rule-based Row Filter may seem confusing. For example, the expression
$StateName$ LIKE "North*" => TRUE
says to return a TRUE value for any StateName value that matches the wildcard expression "North*". Any record that does not match this expression will automatically have a FALSE value and not pass through the node.
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You may also write multiple expressions across multple lines. Each line is treated independently, so you can think of them as a logical OR construct.
$StateName$ = "Florida" => TRUE
$StateName$ = "New Mexico" => TRUE
will pass records that match either Florida OR New Mexico, but no others.
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Each rule is comprised of two parts:
- The condition, known as the antecedent. This is the left-hand side of the expression.
- The outcome, known as the consequent. This is the right-hand side of the expression after the => symbol.
Workflow
Rule-based Row Filter
Used extensions & nodes
Created with KNIME Analytics Platform version 4.7.2
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