Table 4.

The c-statistic of logistic regression model showing the performance of spectral indices in discriminating between the healthy (T0) and disease (T1) treatments of the four reference varieties [bold font highlights c-values ≥ 0.8 for the early (Weeks 1–3, heading to fruiting stages) and later stages (Weeks 4–6, ripening stage)].

Index	C-statistic
	Weeks 1–3	Weeks 4–6	All
SRRed−edge	0.77	0.54	0.59
CIRed−edge	0.78	0.54	0.59
NDVI	0.79	0.58	0.61
ND705	0.77	0.54	0.59
mSR705	0.77	0.51	0.58
mND705	0.77	0.51	0.58
SIPI	0.80	0.55	0.61
PRI	0.77	0.71	0.54
WI	0.84	0.70	0.68
NDWI	0.92	0.80	0.74
PSRI	0.82	0.43	0.58
RRDIRed−edge	0.72	0.60	0.57
NPQI	0.70	0.83	0.70
CAI	0.83	0.61	0.64
HI	0.80	0.76	0.54
DSI	0.62	0.79	0.56