This node allows you to derive new output column data. You can perform simple mathematical expressions based on the input columns data. The resulting data is processed on a row-per-row basis.
- Input Data Columns section allows you to analyse what input data columns are incomming into the node. The list will show an extra field indicating the variable name assigned to each column (ie: V0,V1,V2,V3,V4,etc).
- Output Derive Columns section allows you to create a new list of columns that will form the output data. This allows you to create columns based on a mathematical expression using the input data columns.
- Adding a Column is done by first entering the name for the new column. You then choose whether the column is a continuous or discrete type. Then you can enter a mathematical expression using the variable names assigned to the input columns and the following mathematical symbols [()+-/*\^]. Click on the Add button to add the new column to the end of the list. Choosing the column to be a discrete type will convert the resulting mathematical expression into a string.
- Changing a Column is done by first selecting the derive column, then alter the entries and finally clicking on the Change button.
- Removing a Column is done by first selecting the column and then clicking on Remove button.
- Shifting a Column is done by first selecting the column and then clicking on the Shift Up or Shift Down buttons.
- Mathematical Expressions. If you form mathematical expressions using variable columns that are discrete then the discrete data values will be converted to numerical values if the discrete values contain the ascii symbols [0123456789.-]. If the discrete values contain characters other than numerical characters the data value will be converted to the numerical value of zero. The mathematical expression will be evaluated with the variable converted to zero. This may cause the evaluation to overflow or divide by zero. If any data contains the missing symbol '?' it will also be converted to numerical zero even if the column is a continuous type.
NOTE: Global Constants can be used within the Expression entry.