Freezing Calculations

Many customers create calculated columns to aide in their analysis.  Calculated columns are static columns, but if the data in the underlying columns, which are used in the calculation, changes, it is recalculated based on the new data. However, TIBCO Spotfire Professional provides a way through which your calculation results can be frozen and these frozen calculations can be used for further analysis. We will use some examples to illustrate its use. Calculated Columns Occasionally, the columns included in a data table may not contain all necessary information for analysis. In those cases, the necessary information can be computed from existing columns by using the mathematical and logical expressions provided by the Insert Calculated Column tool.  

For our example, we will use a simple data table with just two columns, both with numeric values, to illustrate use of frozen calculations.

Using mathematical and logical expression we calculated a new column called 'Result Calculation' as shown below:

If there is a situation where data for First and Second column changes, our calculated column will also get updated based on new data values as shown below:

 

As mentioned before, it is possible that you will want to keep your  original result calculation (based on our earlier data) and you will want to calculate a new result calculation based on the new column values. You may also want to compare the two result columns. If we freeze the calculated column, the data will not change, even if the data from the source columns changes.

 

Freezing calculations

In order to freeze a calculated column, click  Edit > Column Properties and select the 'Freeze Column' button.  

By freezing calculated columns, you can also perform analysis across multiple data tables. Suppose you have an analysis file with the following two data tables:

 

There is a common column in both data tables (Row no), and one of the data tables has a frozen calculated column (result calculation). Based on  [Result calculation] in example data table we want to create another calculated column in Second data table  .We can use Insert >columns from external data to perform this calculation  and in this case depending on our requirements we may like to have result calculation values frozen.Replace data table If you try to replace the example data table with the second data table, only the imported columns would be available for matching. Your calculated columns from the example data table are not visible.  If the calculated column is frozen, it will become visible in the matching columns dialog since the column values are frozen.   

Interested in learning more about calculated columns? Attend our SP131 Spotfire Essentials course onsite, regionally at one of our training centers, or using our blended training.