I would like to intergrate a couple of polygons into my leaflet map. These polygons are written in WKT. By using the package wellknown i convert them to a geosjon format
InstallCandidates <-c("jsonlite","leaflet","wellknown","rgdal","sp")
toInstall<-InstallCandidates[!InstallCandidates %in% library()$results[,1]]
if(length(toInstall) !=0){install.packages(toInstall,repos="http://cran.r-project.org")}
lapply(InstallCandidates,library,character.only=TRUE)
rm("InstallCandidates","toInstall")
url<- "https://kaart.amsterdam.nl/datasets/datasets-item/t/cora-geplande-wegwerkzaamheden/export/json"
werkzaamheden <- as.data.frame(fromJSON(url))
The var linestring is one WKT object in this url.
linestring<- "LINESTRING (4.9473233812748 52.304767613036, 4.9473234970894 52.304755910603, 4.947323612904 52.30474420817, 4.9473350439563 52.304746591253, 4.9473310174218 52.304767641433, 4.9473119270542 52.304767570438)"
locatie<- wkt2geojson(linestring, feature = FALSE)
class(locatie)
Is tried to plot this linestring in a leaflet object by doing this:
leaflet(data = locatie) %>%
addTiles() %>%
addGeoJSON(geojson =locatie, color = "red",fill = "red")
But i dont see the linestring, could anyone help me pleas?
Thanks
Related
I'm trying to plot the boundaries of the localities of Brussels. The system of coordinates of my json file has to be converted to a longlat system to display the Polygons on Folium maps. The issue I get is that my coordinates are projected into the Pacific ocean. I guess it is probably due to the fact that the parameters I set are not the good ones. Please find below my code:
import json
import pyproj
import folium
# Load JSON file
with open("districts.json", "r") as f:
data = json.load(f)
# Create a transformation object
in_proj = pyproj.Proj(proj='utm',zone=31,datum='WGS84')
out_proj = pyproj.Proj(proj='longlat',datum='WGS84')
# Transform the coordinates
features = data["features"]
for feature in features:
coords = feature["geometry"]["coordinates"][0]
coords = [pyproj.transform(in_proj, out_proj, coord[0], coord[1]) for coord in coords]
feature["geometry"]["coordinates"] = [coords]
# Plot the polyggon on a map
m = folium.Map()
folium.GeoJson(data).add_to(m)
m
This corresponds to how my json file is structured:
{"type":"FeatureCollection","features":[{"geometry":{"type":"Polygon","coordinates":[[[152914.748398394,173305.19242333],[152947.4133984,173326.530423339],...,[152961.983398418,173225.325423267],[152914.748398394,173305.19242333]]]},...
(https://i.stack.imgur.com/SuU4Q.png)
(https://i.stack.imgur.com/oIKJN.png)
Does anyone has an idea how to solve this? How could I find the right parameters?
I tried different zones but I would rather know of to find the right zone number and understand how it works.
I'm having a problem when trying to scrape an image from this page. My code is as follow:
library(rvest)
url <- read_html("https://covid-19vis.cmm.uchile.cl/chart")
m <- '/html/body/div/div/div[4]/main/div/div/div/div/div/div[2]/div[1]'
grafico_cmm <- html_node(url, xpath = m) %>% html_attr('src')
When I run the above code, the result is NA. Does someone know how can I scrape the plot or maybe the data from the page?
Thanks a lot
It not an image, it is an interactive chart. For an image, you would need to scrape the data points and re-create as a chart and then convert to an image. Xpath is also invalid.
The data comes from an API call. I checked the values against the chart and this is the correct endpoint.
library(jsonlite)
data <- jsonlite::read_json('https://covid-19vis.cmm.uchile.cl/api/data?scope=0&indicatorId=57', simplifyVector = T)
The chart needs some tidying but here is a basic plot of the r values:
data$date <- data$date %>% as.Date()
library("ggplot2")
ggplot(data=data,
aes(x=date, y=value, colour ='red')) +
geom_line() +
scale_color_discrete(name = "R Efectivo", labels = c("Chile"))
print tail(data)
I have been working with Leaflet for creating cool interactive maps in R. However, I cannot export the maps, as the background map ends up being grey after export.
library(leaflet)
library(htmlwidgets)
m <- leaflet(data.frame(lat = 55.71654, lng = 12.47484))
m <- addCircles(m, popup = "testpopup")
m <- addTiles(m)
m
saveWidget(m, file="testmap.html", selfcontained = TRUE)
Is there an alternative to Leaflet where you can export your interactive maps as HTML? Or do I have to get into the whole Leaflet/Shiny thing?
As mentioned my #Martin Schmelzer then it all works after updating leaflet through the devtools::install_github('rstudio/leaflet'). Thanks.
I have a JSON file of a long route. The file contains the lat and long of of this route.
I'm trying to mark different sections of this route based on a set of criteria (which I've compiled in a dataframe). However, I'm facing to problems:
1) How do I break up this long set of lat and longs into segments? (can't do this manually because I have many route variations)
2) How do I assign a variable color to each segment?
I intend to use leaflet map (for its interactivity), but I'm open to better suggestions.
When working with spatial data, it helps to know spatial classes! I am assuming you know hoe to read your JSON file as a data frame into R.
Here's a reproducible example:
library(mapview)
library(sp)
### create some random data with coordinates from (data("breweries91", package = "mapview"))
set.seed(123)
dat <- data.frame(val = as.integer(rnorm(32, 10, 2)),
lon = coordinates(breweries91)[, 1],
lat = coordinates(breweries91)[, 2])
### state condition for creation of lines
cond <- c(8, 9, 10)
### loop through conditions and create a SpatialLines object for each condition
lns <- lapply(seq(cond), function(i) {
ind <- dat$val == cond[i]
sub_dat <- dat[ind, ]
coords <- cbind(sub_dat$lon, sub_dat$lat)
ln <- coords2Lines(coords, ID = as.character(cond[i]))
proj4string(ln) <- "+init=epsg:4326"
return(ln)
})
### view lines with mapview
mapview(lns[[1]], col = "darkred") +
mapview(lns[[2]], col = "forestgreen") +
mapview(lns[[3]], col = "cornflowerblue")
Essentially, what we are doing here is create a valid sp::SpatialLines object for each condition we specify. The we plot those using mapview given you mentioned interactivity. Plotting of spatial objects can be achieved in many ways (base, lattice, ggplot2, leaflet, ...) so there's many options to choose. Have a look at sp Gallery for a nice tutorial.
Note: This answer is only valid for non-projected geographic coordinates (i.e. latitude/longitude)!
I have a script which allows me to generate a map with with "R for leaflet" :
library(htmlwidgets)
library(raster)
library(leaflet)
# PATHS TO INPUT / OUTPUT FILES
projectPath = "path"
#imgPath = paste(projectPath,"data/cea.tif", sep = "")
#imgPath = paste(projectPath,"data/o41078a1.tif", sep = "") # bigger than standard max size (15431804 bytes is greater than maximum 4194304 bytes)
imgPath = paste(projectPath,"/test.tif", sep = "")
outPath = paste(projectPath, "/leaflethtmlgen.html", sep="")
# load raster image file
r <- raster(imgPath)
# reproject the image, if necessary
#crs(r) <- sp::CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs")
# color palette, which is interpolated ?
pal <- colorNumeric(c("#FF0000", "#666666", "#FFFFFF"), values(r),
na.color = "transparent")
# create the leaflet widget
m <- leaflet() %>%
addTiles() %>%
addRasterImage(r, colors=pal, opacity = 0.9, maxBytes = 123123123) %>%
addLegend(pal = pal, values = values(r), title = "Test")
# save the generated widget to html
# contains the leaflet widget AND the image.
saveWidget(m, file = outPath, selfcontained = FALSE, libdir = 'leafletwidget_libs')
My problem is that this is generating a html file and I need this map to be dyanamic. For example, when a user click on some html button which is not integrate on the map, I want to add a rectangle on the map. Any solutions would be welcome...
Leaflet itself does not provide the interactive functionality you are looking for. One solution is to use shiny, which is a web application framework for R. From simple R code, it generates a web page, and runs R on the server-side to respond to user interaction. It is well documented, has a gallery of examples, and a tutorial to get new users started.
It works well with leaflet. One of the examples on the shiny web site uses it, and also includes a link to the source code.
Update
Actually, if simple showing/hiding of elements is enough, leaflet alone will suffice with the use of groups. From the question it's not very clear how dynamic you need it to be.