Spline interpolation for demographic variables: the monotonicity problem

 

In demography, it is often necessary to obtain a monotonic interpolation of data. A solution to this problem is available using the Hyman filter for cubic splines. However, this does not seem to be well-known amongst demographers, and no implementation of the procedure is readily available. We remedy these problems by outlining the relevant ideas here, and providing a function for the R package.

R code

Cite

@article{SHW04,
  author  = {Len Smith and Rob J Hyndman and Simon N Wood},
  doi     = {10.1007/BF03032212},
  journal = {J Population Research},
  number  = {1},
  pages   = {95--98},
  title   = {Spline interpolation for demographic variables: the monotonicity problem},
  volume  = {21},
  year    = 2004
}