To cite package 'ipdw' in publications use:

Stachelek J (2019). ipdw: spatial interpolation by Inverse Path Distance Weighting. . R package version 0.2-8, https://cran.r-project.org/package=ipdw.

Corresponding BibTeX entry:

  @Manual{,
    title = {ipdw: spatial interpolation by Inverse Path Distance
      Weighting. },
    author = {Joseph Stachelek},
    year = {2019},
    note = {R package version 0.2-8},
    url = {https://cran.r-project.org/package=ipdw},
  }