Regression Analysis, R Squared, Pseudo R Squared, Adjusted R Squared, Deviance.
As mentioned earlier: D(y, y_pred) = Deviance of the fitted nonlinear model D(y, y_mean) = Deviance of the Intercept-only model (a.k.a. the null-model). The null model contains only the intercept i.e. no regression variables. Using our formula for Deviance: Deviance of a fitted regression model