“I have experimental data for absorption (dependent variable) measured at various wavelengths (independent variable). Now I want estimates of the absorption at other values in the same range.” This is an interpolation problem. We wish to obtain the value of a dependent value at point for which we did not sample the independent value. Interpolation is a mathematical procedure for filling in the gaps between available values. SciPy provides a module for interpolation based on the FITPACK library of FORTRAN functions. (Thus, it is fast and reliable.) A Simple Example To gain access to the interpolation functions, import the module: import scipy.interpolate Or, simply import the function we need for our one-dimensional problem: from scipy.interpolate import interp1d Suppose that each column of an array expData contains a (wavelength, absorption) pair. We can use interp1d to create a function-like object for interpolation from this data set: F = interp1d(expData[:,0], ex