This node allows you to select which rows of data you wish to pass through to the output. This is done by setting up logical expressions based on what the data values in given columns are.
- Output Data Columns section allows you to analyse the incomming data, it will list the columns available to the node.
- Select Logic section allows you to specify logical expressions which are used to evaluate whether a given input data row will be passed to the output.
- The list shows the sequence of logical expressions and is read in the order as shown. You can have more than one logical expression following another. If any one logical expression evaluates to TRUE then the current row been processed will be passed to the output. For the example shown: if C1>0 and C2>0 or C1>1 then pass the row to the output.
- To begin a new expression, first click on one column in the Data Columns list. This will highlight the Add button. The columns name will be placed in the left hand text box. You can then select the approriate logical condition and enter a number or string depending on the columns data type. You also have to choose the AND, OR if you wish to continue with a another logical condition or OUT as an termination to the logical expression. Finaly clicking on Add will enter the new logical condition to the end of the current list.
- To change a logical condition first select the condition in the list. Then change the conditional logic. The changes will be reflected in the list when you click on the Change button. You can also use the Remove button to remove the selected condition. You can also use the Shift Up and Shift Down buttons to move the condition with in the list.
- Since some data values contain missing values (ie: ?) and that you can compare data values to a missing value, the following logic is applyed to both discrete and continuous column types:
Data Value
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Conditional Value
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Result
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10
|
?
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Always True - Conditional Logic is NOT Checked
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?
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?
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Check with Conditional Logic
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?
|
10
|
Always True - Conditional Logic is NOT Checked
|
10
|
10
|
Check with Conditional Logic
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The reason for this logic is that if you were to replace the missing value with a suitable value you could always pick a value that will make the conditional logic chosen result in a answer of True.
NOTE: Global Constants can be used within the Logical Compare Value entry.
