R shiny leaflet add crosses for points - r

Question

I am trying to represent points as a cross (+) on a leaflet map. I have started following the example here. There are two things I would like to sort out;
1) why all the points are not showing up as crosses.
2) Can I fix the marker size, so that when I zoom out or in the markers stay the size of the initial creation, ie. not dynamic markers. Currently if I zoom out they get large but I want to avoid that.
Reproducible code below.
Poly = data.frame(Strat = c("A","A","A","A","A","B","B","B","B","B"), long = c(174.5012, 174.5026, 174.5026, 174.5014,174.5012,174.5012 ,174.5020, 174.5020,174.5012,174.5012),lat = c(-35.84014, -35.84018, -35.84137,-35.84138,-35.84014,-35.84014,-35.84014,-35.84197,-35.84197,-35.84014))
Points = data.frame(long = c(174.5014 ,174.5017, 174.5021, 174.5023, 174.5020, 174.5017 ,174.5021 ,174.5017, 174.5021, 174.5019), lat = c(-35.84187, -35.84165, -35.84220 ,-35.84121, -35.84133, -35.84034, -35.84082, -35.84101, -35.84112, -35.84084))
library('leaflet')
library('shiny')
library('webshot')
library('htmlwidgets')
# A function to create png images for each shape and color
# for the leaflet maps
pchIcons = function(pch = 1, width = 30, height = 30, bg = "transparent", col = "black", ...) {
n = length(pch)
files = character(n)
# create a sequence of png images
for (i in seq_len(n)) {
f = tempfile(fileext = '.png')
png(f, width = width, height = height, bg = bg)
par(mar = c(0, 0, 0, 0))
plot.new()
points(.5, .5, pch = pch[i], col = col[i], cex = min(width, height) / 8, ...)
dev.off()
files[i] = f
}
return(list("iconUrl" = files, "iconWidth" = width, "iconHeight" = height))
}
##### UI
ui <- fluidPage(
mainPanel(leafletOutput("map"))
)
##### Server
server = function(input, output){
output$map <- renderLeaflet({
mymap()
})
mymap <- reactive({
leaflet() %>% addTiles(urlTemplate = "http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png", attribution = NULL, layerId = NULL, group = NULL, options = tileOptions()) %>%
clearShapes() %>%
clearMarkers() %>%
fitBounds(lng1 = 174.5042, lat1= -35.83814,lng2= 174.5001, lat2 = -35.8424)
})
myfun <- function(map) {
print("adding points")
map %>% clearShapes() %>%
clearControls() %>%
clearMarkers() %>%
addCircles(lng = Points$long, lat = Points$lat, color = "blue",fillOpacity = 1,radius = 1) %>%
addMarkers(lng = Points$long, lat = Points$lat,icon = makeIcon(iconUrl = pchIcons(pch= 3,col="blue", height = 20, width = 20),popupAnchorX = 10, popupAnchorY = 0))
}
AddStrataPoly <- function(map) {
print("adding polygons")
for(i in 1:length(unique(Poly$Strat))) {
map <- map %>% addPolygons(lng = Poly[Poly$Strat == unique(Poly$Strat)[i],]$long, lat = Poly[Poly$Strat == unique(Poly$Strat)[i],]$lat, layerId = unique(Poly$Strat)[i], color = 'gray60', options = list(fillOpacity = 0.1))
}
map
}
observe({
leafletProxy("map") %>% myfun() %>% AddStrataPoly()
})
newmap <- reactive({
mymap() %>% myfun() %>% AddStrataPoly()
})
}
shinyApp(ui, server)

Answer 1

Try this (skipping the two dataframes Poly and Points to keep it shorter):
library('leaflet')
library('shiny')
library('webshot')
library('htmlwidgets')
# A function to create png images for each shape and color
# for the leaflet maps
pchIcons = function(pch = 3,
width = 30,
height = 30,
bg = "transparent",
col = "black",
...) {
n = length(pch)
files = character(n)
# create a sequence of png images
for (i in seq_len(n)) {
f = tempfile(fileext = '.png')
png(f,
width = width,
height = height,
bg = bg)
par(mar = c(0, 0, 0, 0))
plot.new()
points(
.5,
.5,
pch = pch[i],
col = col[i],
cex = min(width, height) / 8,
...
)
dev.off()
files[i] = f
}
return(list(iconUrl = files, iconWidth = width, iconHeight = height))
}
##### UI
ui <- fluidPage(mainPanel(leafletOutput("map")))
##### Server
server = function(input, output) {
output$map <- renderLeaflet({
mymap()
})
mymap <- reactive({
leaflet() %>% addTiles(
urlTemplate = "http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png",
attribution = NULL,
layerId = NULL,
group = NULL,
options = tileOptions()
) %>%
clearShapes() %>%
clearMarkers() %>%
fitBounds(
lng1 = 174.5042,
lat1 = -35.83814,
lng2 = 174.5001,
lat2 = -35.8424
)
})
myfun <- function(map) {
print("adding points")
map %>% clearShapes() %>%
clearControls() %>%
clearMarkers() %>%
addCircles(
lng = Points$long,
lat = Points$lat,
color = "blue",
fillOpacity = 1,
radius = 1
) %>%
addMarkers(
lng = Points$long,
lat = Points$lat,
icon = makeIcon(
iconUrl = pchIcons()$iconUrl,
iconWidth = pchIcons()$iconWidth,
iconHeight = pchIcons()$iconHeight,
popupAnchorX = 10,
popupAnchorY = 0
)
)
}
AddStrataPoly <- function(map) {
print("adding polygons")
for (i in 1:length(unique(Poly$Strat))) {
map <-
map %>% addPolygons(
lng = Poly[Poly$Strat == unique(Poly$Strat)[i], ]$long,
lat = Poly[Poly$Strat == unique(Poly$Strat)[i], ]$lat,
layerId = unique(Poly$Strat)[i],
color = 'gray60',
options = list(fillOpacity = 0.1)
)
}
map
}
observe({
leafletProxy("map") %>% myfun() %>% AddStrataPoly()
})
newmap <- reactive({
mymap() %>% myfun() %>% AddStrataPoly()
})
}
shinyApp(ui, server)