is a 1 ×2 matrix of endpoint values. Slopes of the two ends of the curve are reported as angles expressed in degrees. The SPLINEC call returns the endval argument. The inputs to the SPLINEC subroutine ...

But [Marb] has an answer for that; after gathering data at each wavelength, he applies a cubic spline interpolation to derive the spectrum. It’s demonstrated in the video below using chlorophyll ...