Leaflet map legend in R Shiny app has doesn't show colors
Earlier I had just a simple snippet that showed how to add legends. I did not use the ~ before the legend values as is the norm. I did the traditional dataframe$column and it works nicely.
This is now updated to see how it all fits together. Here is a full-fledged mapping run after creating all of the variable cuts, etc. The final cleansed data frame was called zipData
# create a full popup
# add some HTML for editing the styles
zipData$popUp <- paste('<strong>',zipData$Street, '</strong><br>',
'TIV = $',prettyNum(zipData$tiv, big.mark = ',',preserve.width = 'none'), '<br>',
'City: ', zipData$city, '<br>',
'YrBuilt = ', zipData$YearBuilt, '<br>',
'Construction = ', zipData$ConstructionCode, '<br>',
'Occupancy = ', zipData$OccupancyCode, '<br>',
'Premium = $' , prettyNum(zipData$Premium, big.mark = ',',preserve.width = 'none') , '<br>',
'GrossArea = ', prettyNum(zipData$GrossArea, big.mark = ',', preserve.width = 'none'), '<br>',
'RoofYr = ', zipData$RoofYearBuilt, '<br>')
# set color scale for key factor
colorsConst <- colorFactor(rainbow(4), zipData$ConstructionCode)
# color scales for numerical bins
colorstivValue <- colorFactor(palette = 'Accent', zipData$tivValueLvl)
colorsYrBuilt <- colorFactor(palette = 'Spectral', zipData$yrBuiltLvl)
colorsRoofYrBuilt <- colorFactor(palette = "YlOrRd", zipData$roofYrBuiltLvl)
# begin the leaflet map construction
# create the map opbject
m <- leaflet() %>%
addTiles() %>%
# add different tiles for different color schemes
addProviderTiles(providers$OpenStreetMap, group = 'Open SM') %>%
addProviderTiles(providers$Stamen.Toner, group = 'Toner') %>%
addProviderTiles(providers$CartoDB.Positron, group = 'CartoDB') %>%
addProviderTiles(providers$Esri.NatGeoWorldMap, group = 'NG World') %>%
setView(lng = -90, lat = 30, zoom = 10) %>%
##############################
# this section is for plotting the variables
# each variable below is a layer in the map
# construction
addCircleMarkers(data = zipData, lat = ~Lat, lng = ~Lon,
color = ~colorsConst(ConstructionCode), popup = zipData$popUp,
radius = 5, group = 'Construction') %>%
# tiv
addCircleMarkers(data = zipData, lat = ~Lat, lng = ~Lon,
color = ~colorstivValue(tivLvl), popup = zipData$popUp,
radius = ~tiv/20000, group = 'Bldg Value') %>%
# year built
addCircleMarkers(data = zipData, lat = ~Lat, lng = ~Lon,
color = ~colorsYrBuilt(yrBuiltLvl), popup = zipData$popUp,
radius = ~YearBuilt/250, group = 'Yr Built') %>%
######################################
# layer control
addLayersControl(
baseGroups = c('Open SM', 'Toner', 'Carto DB', 'NG World'),
overlayGroups = c('Construction',
'TIV',
'Yr Built'
),
options = layersControlOptions(collapsed = F)
) %>%
#################################################
add the legends for each of the variables
# construction
addLegend('bottomright', pal = colorsConst, values = zipData$ConstructionCode,
title = 'Construction Code',
opacity = 1) %>%
# tiv
addLegend('bottomleft', pal = colorstivValue, values = zipData$tivLvl,
title = 'TIV',
opacity = 1) %>%
# year built
addLegend('topleft', pal = colorsYrBuilt, values = zipData$yrBuiltLvl,
title = 'Yr Built',
opacity = 1)
m # Print the map
A portion of the map is shown below.
I was able to make the colors showing up by changing the way I was referencing the values column in the arguments of the AddLegend function. I put the stat.selected variable in double brackets, which seemed to fix the problem:
addLegend(position = "bottomleft",
pal = pal, values = shp.data()[[stat.selected]],
title = "Legend",
opacity = 1
)
For clarification, the stat.selected variable comes from the following switch statement:
stat.selected <- isolate(switch(input$var.stat,
"Total employment" = "tot_emp",
"Mean annual wage" = "a_mean",
"Mean hourly wage" = "h_mean",
"Location quotient" = "loc_quotient"
)
where "tot_emp", "a_mean", "h_mean", and "loc_quotient" are column names in the shp.data spatial polygons data frame.
I guess the problem was that I was trying to pass in the column name by variable using a $.
I'm still a fairly novice R user, so if anyone can explain why the example in the Leaflet for R documentation does not work in this case I would appreciate it.
I had the same message
Error in UseMethod("doResolveFormula") : no applicable method for 'doResolveFormula' applied to an object of class "NULL"
with
data <- data.frame(lng1 = c(1, 2, 3),
lng2 = c(2, 3, 4),
lat1 = c(1, 2, 3),
lat2 = c(2, 3, 4),
values = c(1, 2, 3))
pal_grid <- colorNumeric(palette = "YlGn", domain = data$values)
leaflet() %>%
addRectangles(lng1 = data$lng1, lat1 = data$lat1,
lng2 = data$lng2, lat2 = data$lat2,
fillColor = ~pal_grid(data$values),
fillOpacity = 0.2,
weight = 2, opacity = 0.5)
The solution is to provide to leaflet the data that you are using to create the element in the main call to leaflet() or in the call to any element that you add after that.
In the main call to leaflet():
data <- data.frame(lng1 = c(1, 2, 3), lng2 = c(2, 3, 4), lat1 = c(1, 2, 3), lat2 = c(2, 3, 4), values = c(1, 2, 3)) pal_grid <- colorNumeric(palette = "YlGn", domain = data$values) leaflet(data = data) %>% addRectangles(lng1 = data$lng1, lat1 = data$lat1, lng2 = data$lng2, lat2 = data$lat2, fillColor = ~pal_grid(data$values), fillOpacity = 0.2, weight = 2, opacity = 0.5)At the moment of add elements:
data <- data.frame(lng1 = c(1, 2, 3), lng2 = c(2, 3, 4), lat1 = c(1, 2, 3), lat2 = c(2, 3, 4), values = c(1, 2, 3)) pal_grid <- colorNumeric(palette = "YlGn", domain = data$values) leaflet() %>% addRectangles(data = data, lng1 = data$lng1, lat1 = data$lat1, lng2 = data$lng2, lat2 = data$lat2, fillColor = ~pal_grid(data$values), fillOpacity = 0.2, weight = 2, opacity = 0.5)`