Coloring continuous data in leaflet, R does not wo

问题:

Here is my data:

t <- data.frame(Name=c('A','B','C','D','E','F','G','H','I','J'),
                Longitude=c(151.2008,151.2458,150.8217,151.1215,150.8906,151.0660,150.8889,150.9188,150.4364,150.9982),
                Latitude=c(-33.90772,-33.89250,-34.05951,-33.97856,-34.40470,-33.90010,-33.92832,-33.90761,-34.44651,-33.79232),
                Diff=c(0.03,0.10,0.12,0.04,-0.12,0.34,-0.14,-0.01,0.21,-0.02),
                Diff1=c(30,100,120,40,-120,340,-140,-10,210,-20))

I want to use leaflet and R to draw this points on the map, and use the values of Diff / Diff1 for continuous color. Here is my code:

library(leaflet)
pal <- colorNumeric(
    palette = colorRampPalette(c('red','green')),
    domain = t$Diff1)
leaflet(data=t) %>%
    addTiles() %>%
    addCircles(lng=~Longitude,lat=~Latitude,radius=10,popup=~Name,color=~pal(Diff1))

I do not need a lot of different colors here. I just want the color could change from red to green as the increase of Diff1. But I only have red points on my map:

Another problem is no matter how I change the value of radius, the size of the data point does not change at all. I have no idea where I got wrong.

So, my questions are:

How to use coutinuous color? How to change the size of the points?

回答1:

Try this (exluding the dataframe t below):

library(leaflet)
pal <- colorNumeric(
  palette = colorRampPalette(c('red', 'green'))(length(t$Diff1)), 
  domain = t$Diff1)

leaflet(data = t) %>%
  addTiles() %>%
  addCircleMarkers(
    lng =  ~ Longitude,
    lat =  ~ Latitude,
    radius = ~ Diff * 100,
    popup =  ~ Name,
    color =  ~ pal(Diff1)
  )

Remember, colorRampPalette actually returns a function, so you need to "crack" open the function with () when you are going to use it, like so:

colorRampPalette(c('red', 'green'))(length(t$Diff1))
# "#FF0000" "#E21C00" "#C63800" "#AA5500" "#8D7100" "#718D00" "#55AA00" "#38C600" "#1CE200" "#00FF00"

Check the start and end colors (should be "red" and "green"):

col2rgb("#FF0000")
#       [,1]
# red    255
# green    0
# blue     0

col2rgb("#00FF00")
#       [,1]
# red      0
# green  255
# blue     0

Yes, it did work out as expected.