A method prepares data for subsequent analysis. The method displays a user interface having a data flow pane, including a flow diagram having a plurality of nodes. Each node specifies one or more operations. The method receives user input to select an existing node in the flow diagram, receives user input to insert a new node into the flow diagram, and receives user input to select a first set of two or more columns of data values from a data set corresponding to the existing node. The method pivots the selected columns to form a modified data set having new rows and new columns. The user selects two or more additional columns, and the method pivots on the additional columns, resulting in a second new column added to the modified data set. Each data value from the additional columns is added to the second new column in a respective row.