Interactive maps {mapview, mapedit} without shiny

interact_map.r

#https://gis.stackexchange.com/questions/253483/leaflet-tool-for-multiple-marker-selection-and-computation-of-summary
# devtools::install_github("r-spatial/mapedit")

library(sf)             # for spatial data type representation
library(mapview)        # for the raster data and quick viewing
library(mapedit)        # for the interaction (selection of the data) 

# create some mock data points in the vicinity of the raster layer
set.seed(42) # to be reproducible
dframe = data.frame(a = 1:50, 
                    b = rnorm(50, 2, 1), 
                    x = runif(50, 11.15, 11.25),
                    y = runif(50, 49.7, 49.75))

# convert data.frame to sf object as we need 
# geo-spatial data type for this kind of objective
# epsg 4326 is geographic longlat 'projection'
dframe_sf = st_as_sf(dframe, coords = c("x", "y"), crs = 4326)

# inspect data on base map
mapview(dframe_sf)

# select features via polygon/rectangle/line/point or the like
# by using the draw tools of the draw toolbar on the left 
# and press "Done" when finished.
# multiple selections are also possible.
# (line/point selection will not work as points have no dimension!)
# mode = "click" will enable selection via clicking on features.
selected = selectFeatures(dframe_sf, mode = "draw")

# check the selection (selected will be diplayed in blue)
mapview(dframe_sf,  col.regions = "red") + selected

# given that selected is a sf object (and hence a data.frame) 
# claculating summaries works just as expected with a normal data.frame
summary(selected)
mean(selected$a)
mean(selected$b)
sd(selected$b)

# we can also set other selection criteria. e.g. invert selection via st_disjoint
diff_selected = selectFeatures(dframe_sf, mode = "draw", op = st_disjoint)

# check the selection (selected will be diplayed in blue)
mapview(dframe_sf, col.regions = "red") + diff_selected