Can't Loop with R's Leaflet Package to Produce Multiple Maps

Can't loop with R's leaflet package to produce multiple maps

Here is a quick way to add leaflet-timeline in the way you suggest. For some reason, the timeline does not render perfectly in RStudio Viewer, but it does seem to work correctly in Chrome. I commented inline in the code to describe the steps.

library(htmlwidgets)
library(htmltools)
library(leaflet)
library(geojsonio)

#Build data.frame with 10 obs + 3 cols
power <- data.frame(
  "Latitude" = c(33.515556, 38.060556, 47.903056, 49.71, 49.041667, 31.934167, 54.140586, 54.140586, 48.494444, 48.494444),
  "Longitude" = c(129.837222, -77.789444, 7.563056, 8.415278, 9.175, -82.343889, 13.664422, 13.664422, 17.681944, 17.681944),
  "start" = do.call(
    "as.Date",
    list(
      x = c("15-Sep-1971", "1-Dec-1971", "1-Feb-1972", "1-Feb-1972", "1-Feb-1972", "1-Feb-1972", "1-Apr-1972", "1-Apr-1972", "24-Apr-1972", "24-Apr-1972"),
      format = "%d-%b-%Y"
    )
  )
)

# set start same as end
#  adjust however you would like
power$end <- power$start

# use geojsonio to convert our data.frame
#  to GeoJSON which timeline expects
power_geo <- geojson_json(power,lat="Latitude",lon="Longitude")

# create a leaflet map on which we will build
leaf <- leaflet() %>%
  addTiles()

# add leaflet-timeline as a dependency
#  to get the js and css
leaf$dependencies[[length(leaf$dependencies)+1]] <- htmlDependency(
  name = "leaflet-timeline",
  version = "1.0.0",
  src = c("href" = "http://skeate.github.io/Leaflet.timeline/"),
  script = "javascripts/leaflet.timeline.js",
  stylesheet = "stylesheets/leaflet.timeline.css"
)

# use the new onRender in htmlwidgets to run
#  this code once our leaflet map is rendered
#  I did not spend time perfecting the leaflet-timeline
#  options
leaf %>%
  setView(44.0665,23.74667,2) %>%
  onRender(sprintf(
    '
function(el,x){
    var power_data = %s;

    var timeline = L.timeline(power_data, {
      pointToLayer: function(data, latlng){
        var hue_min = 120;
        var hue_max = 0;
        var hue = hue_min;
        return L.circleMarker(latlng, {
          radius: 10,
          color: "hsl("+hue+", 100%%, 50%%)",
          fillColor: "hsl("+hue+", 100%%, 50%%)"
        });
      },
      steps: 1000,
      duration: 10000,
      showTicks: true
    });
    timeline.addTo(HTMLWidgets.find(".leaflet"));
}
    ',
    power_geo
))

How to add multiple polygons in leaflet map using r loop?

Here's a solution using packages sf and mapview. Note that this is currently only possible using the develop version of mapview (see commented out devtools::install_github()

# devtools::install_github("r-spatial/mapview@develop")
library(sf)
library(mapview)
library(raster)

countries_1 <- c('PAK','TUR','BGR')

dat_list = lapply(countries_1, function(i) {
  st_as_sf(getData("GADM", country = i, level = 0))
})

m = leaflet() %>% addTiles()

for (i in dat_list) {
  m = mapview::addFeatures(map = m, 
                           data = i, 
                           weight = 3, 
                           fillColor = 'purple', 
                           color = 'purple')
}

m

Note that addFeatures is type agnostic, so any combination of points, lines and/or polygons will work here.

How to render leaflet-maps in loops in RMDs with knitr

You need to put things in a tagList, and have that list print from the chunk. This just uses default settings for fig.show and results; it also uses the htmltools::h3() function to turn the title into an HTML title directly, not using the Markdown ### marker. (You might want h2 or h4 instead.)

---
title: "test3"
output: html_document
---

```{r setup, include=FALSE}
library(leaflet)
library(htmltools)
knitr::opts_chunk$set(echo = TRUE)
```

## Title 1

```{r echo=FALSE}
html <- list()
for (i in 1:4) {
  html <- c(html, 
            list(h3(paste0("Map Number ", i)),
                 leaflet() %>%
                 addTiles() %>%  # Add default OpenStreetMap map tiles
                 addMarkers(lng=174.768, lat=-36.852, popup="The birthplace of R")  
                 )
            )
}
tagList(html)
```

How can rpubs with leaflet maps be made to output full screen?

The second example was published directly from the map in RStudio Viewer. That is, you run the code in the R console, generate the map (which is an HTML widget) in the Viewer, click the Publish button, and publish it to RPubs:

It is not straightforward to generate a full screen HTML widget in R Markdown. You will have to use some CSS (to get rid of margins). I don't have time to provide the full CSS code (the answer in the first paragraph might be what you actually want). To begin with, you need to use the chunk option out.width = '100%' to make sure the map takes the full width of the container.

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