Linear interpolation - Wikipedia
https://en.wikipedia.org/wiki/Linear_interpolationIf the two known points are given by the coordinates (,) and (,), the linear interpolant is the straight line between these points. For a value x in the interval (,), the value y along the straight line is given from the equation of slopes =, which can be derived geometrically from the figure on the right. It is a special case of polynomial interpolation with n = 1.