Abstract: Disclosed herein are, at least in part, methods of determining a tumor fraction of a sample from a subject. The methods can include, for example, acquiring a value for a target variable associated with a subgenomic interval in the sample; determining, from the target variable, a certainty metric; accessing a determined relationship between a stored certainty metric and a stored tumor fraction; and determining, with reference to the certainty metric and the determined relationship, the tumor fraction of the sample.