I always like to download the files available for one of the interesting parts of the conference: "The Shootout Challenge".
Thanks to the IDRC, to put the data files in their webpage in different formats for downloading (Excel, csv, Matlab,Unscrambler and JDX.
More information about the Conference is available at:
The Council For Near-Infrared Spectroscopy: IDCR 2014
These are the spectra on the CAL Data Set 1 imported into R:
We have to check in a plot appart the other zone, to check better the bands there:
Shootout rules say that the spectra include the NIR and IR apectra , and:
"The samples correspond to oils from petroleum reservoirs around the world. These particular spectra were collected in the laboratory at various conditions of pressures and temperatures, in transmittance, using a high pressure flow cell. It should be noted that as pressure and temperature change, so does the effective path length and the density of the fluid. The nominal path length was 1 mm. The temperature and pressure at which the spectra were acquired are provided, and the path length can be calculated using the equation:
d (mm) = 0.8801 + 0.000402065 × T(Kelvin) + 0.00060493 × P(MPa)
Note that in the dataset, the temperatures are in degree C and pressures in psi".
It is clear that the pressure and temperature affect the efective pathlength, so this can be the reason we see different groups of spectra.
The rules also say:
"While most spectra represent mixtures, some pure components are provided, but not identified as such. No pure components are present in the test and validation sets".
So it is also important to detect these pure components.