To cite package 'ipdw' in publications use:

Joseph Stachelek (2016). ipdw: spatial interpolation by Inverse Path Distance Weighting. R package version 0.2-4.

Corresponding BibTeX entry:

  @Manual{,
    title = {ipdw: spatial interpolation by Inverse Path Distance
      Weighting. },
    author = {Joseph Stachelek},
    year = {2016},
    note = {R package version 0.2-4},
    url = {http://CRAN.R-project.org/package=ipdw},
  }