IR spectroscopy, who depended on assignment of absorption bands to specific bond types, were frustrated by the complexity of the region. However, as a quantitative tool, the lower molar absorption levels in the region tended to keep absorption maxima "on-scale", enabling quantitative work with little sample preparation. The techniques applied to extract the quantitative information from these complex spectra where unfamiliar to analytical chemists, and the technique was viewed with suspicion in academia. Generally, a quantitative NIR analysis is accomplished by selecting a group of calibration samples, for which the concentration of the analyte of interest has been determined by a reference method, and finding a correlation between various spectral features and those concentrations using a chemometric tool. The calibration is then validated by using it to predict the analyte values for samples in a validation set, whose values have been determined by the reference method but have not been included in the calibration. A validated calibration is then used to predict the values of samples. The complexity of the spectra are overcome by the use of multivariate calibration. The two tools most often used a multi-wavelength linear regression and partial least squares. Applications Typical applications of NIR spectroscopy include the analysis of food products, pharmaceuticals, combustion products, and a major branch of astronomical spectroscopy. Astronomical spectroscopy Near-infrared spectroscopy is used in astronomy for studying the atmospheres of cool stars where molecules can form. The vibrational and rotational signatures of molecules such as titanium oxide, cyanide, and carbon monoxide can be seen in this wavelength range and can give a clue towards the star's spectral type. It is also used for studying molecules in other astronomical contexts, such as in molecular clouds where new stars are formed. The astronomical phenomenon known as reddening means that near-infrared wavelengths are less affected by dust in the interstellar medium, such that regions inaccessible by optical spectroscopy can be studied in the near-infrared. Since dust and gas are strongly associated, these dusty regions are exactly those where infrared spectroscopy is most useful. The near-infrared spectra of very young stars provide important information about their ages and masses, which is important for understanding star formation in general. Astronomical spectrographs have also been developed for the detection of exoplanets using the Doppler shift of the parent star due to the radial velocity of the planet around the star. Agriculture Near-infrared spectroscopy is widely applied in agriculture