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Do you need to perform a spatial interpolation on point data using an interactive graphical interface? You can exploit GUInterp:

1. try it at https://ranghetti.shinyapps.io/guinterp/;
2. install the {guinterp} package with the command remotes::install_github("ranghetti/guinterp");
3. launch guinterp::guinterp();
4. enjoy.

A typical spatial interpolation workflow includes common steps:

• filtering them to exclude undesired outlier values;
• setting the interpolation method and parameters;
• defining an output raster grid;
• processing data.

All these operations can be performed in R using packages {gstat} and {sf}, but programming skills and manual intervention (to set filters and define the semivariogram model) are required.

For this reason, the availability of an interactive interface can 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. It is a free Shiny interface, released as R package (source code is available here). The page http://guinterp.ranghetti.info/ includes instructions to install and use it; basically, the following four lines of code are sufficient to install the package {guinterp}, load the library and launch the GUI:

install.packages("remotes")
remotes::install_github("ranghetti/guinterp")
library(guinterp)
guinterp()

With GUInterp you can load a point dataset (in spatial or tabular format) and an additional polygon layer with borders; done that, data are visualised on a histogram and on a map (both of them are interactive, thanks to {leaflet} and {plotly} capabilities). Widgets can be used to filter points basing on distribution values, distance from polygon borders or manual selections. If you choose to interpolate them using an Ordinary Kriging, an interface can be used to define the semivariogram. Other selectors allow defining the output raster grid and to tune computation speed.

GUInterp is released as R package under the GNU GPL-3 license. It was presented for the first time at eRum 2020 conference (18th June 2020). If you want to try it before installing, you can run the Shinyapps demo at https://ranghetti.shinyapps.io/guinterp/.