This node provides the possibility to append an
arbitrary number of
columns or modify existing columns using expressions.
For each column
that shall be appended or modified a separate expression
These expressions can be simply created using predefined functions
Nodes. Nevertheless there is no restriction on the number of lines
expression has and the number of functions it uses. This allows
user to create their own complex expressions.
Additionally, intermediate results of functions or calculations can be stored within an expression by assigning them to variables (using '='). This allows results to be reused in different parts of the expression after they have been assigned (see Examples). Note: the names of these variables must be different from all of the names of the predefined functions. Otherwise an error will occur.
To add/remove an expression, the "+"/ "-" buttons respectively have to be used. To edit an expression for an output column, the expression has to be selected in the list of expressions and can be modified in the Expression Editor.
The created expressions are executed row-wise on the input data. Available flow variables and columns of the input table can be accessed via the provided access functions variable("variableName") and column("columnName"). Newly created columns are appended in the order they were defined (top to bottom) whereas replaced columns will remain at the original position of the input table. For each expression the last computed instruction will be returned.
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To use this node in KNIME, install the extension KNIME Expressions from the below update site following our NodePit Product and Node Installation Guide:
A zipped version of the software site can be downloaded here.
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