R sf simple features with quakes data, st_make_grid, dplyr, mapview zcol

code.R

library(sf)
library(dplyr)
library(mapview)
library(mapedit)

qk_mx <- data.matrix(quakes[,2:1])
qk_mp <- st_multipoint(qk_mx)
qk_sf <- st_sf(st_cast(st_sfc(qk_mp), "POINT"), quakes, crs=4326)

grd <- st_sf(geom=st_make_grid(qk_sf), crs=4326)

grd_mut <- grd %>%
  # add id
  mutate(id = 1:n()) %>%
  # calculate
  #  index of quakes contained in grid rect
  #  number of quakes in grid rect
  #  mean mag of quakes in grid rect
  mutate(
    qk_contained = lapply(st_contains(st_sf(geom), qk_sf), identity),
    n_quakes = sapply(qk_contained,length),
    mean_mag = sapply(
      qk_contained,
      function(x) {
        mean(qk_sf[x,]$mag)
      }
    )
  ) #%>%
  # make n_quakes NA if 0
  #mutate(
  #  n_quakes = ifelse(n_quakes==0, NA, n_quakes),
  #  mean_mag = ifelse(is.nan(mean_mag), 0, mean_mag)
  #)

mapview(grd_mut, zcol="n_quakes", na.color="gray", legend=TRUE)

# as edzer highlights there is only na.color and not na.alpha
mapview(grd_mut, zcol="mean_mag", na.color="white", legend=TRUE)

The mapview addLargeFeatures mode does not work properly in this case as the png state is cropped at the dateline. A long standing issue with leaflet/mapview. In fact, the very first reported issue on mapview is still open :-( r-spatial/mapview#6