A method executes at a computing device that includes a display, one or more processors, and memory. The method includes receiving user input to specify a data source. The method includes receiving a first user input in a first region of a graphical user interface to specify a natural language command related to the data source. The device determines, based on the first user input, that the natural language command includes a table calculation expression. In accordance with the determination, the method identifies a second data field in the data source, Values of the first data field are aggregated for each of the time periods in a range of dates according to the second data field. A respective difference between the aggregated values for each consecutive pair of time periods is computed. A data visualization is generated and displayed.