4
800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800
Wavelength (nm)
-2
-1
0
1
2
3
4
5
Category 1
Category 2
Category 3
Category 4
Category Coal
Figure 2. Raw NIR Spectra
900 1000 1100 1200 1300 1400 1500 1600 1700
Wavelength (nm)
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
Category 1
Category 2
Category 3
Category 4
Figure 3. Pre-processed NIR Spectra
Absorbance
Absorbance