Table 6.
Urinary predictor variables selected and the associated R2 and Mallows’ Cp statistics for the RSQUARE selection method, and urinary predictor variables selected by the stepwise selection method for predicting the natural log of struvite relative supersaturation.
| Number of Variables | Selection method: RSQUARE | R 2 | Mallows’ Cp | Selection method: stepwise |
|---|---|---|---|---|
| 1 | pH | 0.659 | 1,196 | pH |
| 2 | pH, magnesium | 0.845 | 414 | pH, magnesium |
| 3 | pH, ammonium, magnesium | 0.884 | 254 | pH, ammonium, magnesium |
| 4 | pH, ammonium, magnesium, citrate | 0.916 | 121 | pH, ammonium, magnesium, citrate |
| 5 | pH, ammonium, phosphorus, magnesium, citrate | 0.936 | 37 | pH, ammonium, phosphorus, magnesium, citrate |
| 6 | pH, ammonium, chloride, phosphorus, magnesium, citrate | 0.940 | 24 | pH, ammonium, chloride, phosphorus, magnesium, citrate |
| 7 | pH, ammonium, chloride, phosphorus, magnesium, citrate, sulfate | 0.943 | 12.2 | pH, ammonium, chloride, phosphorus, magnesium, citrate, sulfate |
| 8 | pH, ammonium, chloride, calcium, phosphorus, magnesium, citrate, sulfate | 0.944 | 8.6 | pH, ammonium, chloride, calcium, phosphorus, magnesium, citrate, sulfate |