I read some papers of risk prediction models, and generally there are three types of measures of the performance: a) Total model performance (e.g. R^2); b) Discrimination; c) Calibration.
However, many papers of risk prediction model only reported the Discrimination and Calibration, seldom reported the R^2. What confused me is that if R^2 is important in risk prediction models. And is there a threshold for the minimal value of R^2 in such models?