1. A method, comprising: at a computer system having one or more processors and memory storing one or more programs configured for execution by the one or more processors: providing a graphical user interface for a user to specify characteristics of a data visualization; receiving, through the provided user interface, user selection of a plurality of fields from a dataset and user association of each field in the plurality of fields with a respective field container in the user interface, wherein the plurality of fields includes a first field and a second field of the dataset, and each field container corresponds to a data visualization characteristic; determining a set of data properties for each of the first and second fields; generating a statistical model of a mathematical relationship between the first and second fields based on the data properties of the first and second fields and data values associated with the first and second fields in the dataset, wherein the mathematical relationship expresses one of the first and second fields as a response variable that is a function of the other of the first and second fields based on the determined set of data properties for the first and second fields; and displaying the data visualization in the user interface according to the user associations of the plurality of fields with the field containers and displaying a graphical representation of the statistical model superimposed on the data visualization.