"GUInterp": a Shiny GUI to support spatial interpolation

In this demo we present "GUInterp", a Shiny interface written to facilitate the operations required to interpolate point data. A typical spatial interpolation workflow includes common steps: loading point data, filtering them to exclude undesired outlier values, setting the interpolation method and parameters, defining an output raster grid and processing data. Interpolation can be conducted in R using dedicated packages; nevertheless, the availability of an interactive interface could be useful to provide additional control during steps requiring user intervention and to facilitate users with low or no programming skills. "GUInterp" was written for this purpose. The user can import input point data, optionally loading a polygon dataset of borders used to constrain the extent of the interpolated outputs. A set of selectors allows filtering input points based on the distribution of the variable to interpolate (which is shown with a reactive histogram) or the spatial position of points (visible on a map). The interpolation can be performed with IDW or Ordinary Kriging methods: in the latter case, the semivariogram can be interactively defined and optimised using a dedicated interface. Further settings can be exploited to tune computation requirements (RAM usage, amount of time) on the basis of available hardware or user needs. "GUInterp" is released as R package under the GNU GPL-3 license.