Table 2 Widely published SRIs with its formulas and relevant references used in this study.

From: Water status and plant traits of dry bean assessment using integrated spectral reflectance and RGB image indices with artificial intelligence

SRI

Formula

References

Normalized water index 1 (NWI-1)

\(\:\frac{{(\text{R}}_{970}-{\text{R}}_{900})}{({\text{R}}_{970}+{\text{R}}_{900})}\)

45

Normalized water index 3 (NWI-3)

\(\:\frac{{(\text{R}}_{970}-{\text{R}}_{880})}{({\text{R}}_{970}+{\text{R}}_{880})}\)

46

Normalized water index 4 (NWI-4)

\(\:\frac{{(\text{R}}_{970}-{\text{R}}_{920})}{({\text{R}}_{970}+{\text{R}}_{920})}\)

47

Normalized water index 5 (NWI-5)

\(\:\frac{{(\text{R}}_{970}-{\text{R}}_{910})}{({\text{R}}_{970}+{\text{R}}_{910})}\)

48

Normalized water index 6 (NWI-6)

\(\:\frac{{(\text{R}}_{780}-{\text{R}}_{670})}{({\text{R}}_{780}+{\text{R}}_{670})}\)

49

Normalized difference index

\(\:{\text{N}\text{D}\text{I}}_{570,\:540}\)

\(\:\frac{{(\text{R}}_{570}-{\text{R}}_{540})}{({\text{R}}_{570}+{\text{R}}_{540})}\)

50

Normalized difference index

\(\:{\text{N}\text{D}\text{I}}_{686,\:620}\)

\(\:\frac{{(\text{R}}_{686}-{\text{R}}_{620})}{({\text{R}}_{686}+{\text{R}}_{620})}\)

50

Anthocyanin index (NAI)

\(\:\frac{{(\text{R}}_{760}-{\text{R}}_{720})}{({\text{R}}_{760}+{\text{R}}_{720})}\)

51

\(\:{\text{N}\text{D}\text{I}}_{780,\:550}\)

\(\:\frac{{(\text{R}}_{780}-{\text{R}}_{550})}{({\text{R}}_{780}+{\text{R}}_{550})}\)

47

\(\:{\text{N}\text{D}\text{I}}_{800,\:670}\)

\(\:\frac{{(\text{R}}_{800}-{\text{R}}_{670})}{({\text{R}}_{800}+{\text{R}}_{670})}\)

52

Pigment-Sensitive Ripening Monitoring Index (PRMI)

\(\:\frac{{(\text{R}}_{750}-{\text{R}}_{678})}{{\text{R}}_{550}}\)

53

Water Index (WI)

\(\:\frac{{\text{R}}_{900}}{{\text{R}}_{970}}\)

54

  1. Where R indicates the reflectance at corresponding wavelength, nm.
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