A method for automatically characterizing plasma during substrate processing is provided. The method includes collecting a set of process data, which includes at least data about current and voltage. The method also includes identifying a relevancy range for the set of process data, wherein the relevancy range includes a subset of the set of process data. The method further includes determining a set of seed values. The method yet also includes employing the relevancy range and the set of seed values to perform curve-fitting, wherein the curve-fitting enables the plasma to be automatically characterized.