Summary
Tableau allows for the creation of additional fields to supplement existing data sets using its calculated fields feature. Calculated fields can range from using simple pieces of logic to manipulate or transform existing fields to complex conditional statements and calculations fixing values at specific levels of aggregation.
Data types in calculated fields must be consistent and so must the aggregation of fields used. When the fields referenced in calculations are not aggregated, then the logic is applied row by row. When the fields are aggregated, then the aggregation takes place first, followed by the logic applied. Calculated fields can also be created without any reference to existing fields; for example, if a single string was to be referenced as a field, that string could be typed into and saved as a calculated field.
Aggregation in calculated fields allows you to pre-aggregate measures as well as to conduct logic on aggregated measures such as dividing one total...