Internal: Create a data frame for predictions (when risk factor is continuous).
predict_df_continuous(riskfactor, q_val, risk_q, data)
A data frame where the distribution continuous risk factor so at an individual level, risk is at the q_val-quantile or below
The name of the risk factor of interest in the dataset
The risk quantile to match to
Estimated risk quantiles
A dataframe containing variables used to fit the model