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I have tried searching for an answer to this question and came across this :

Manually adding legend values in leaflet

But this isn't quite what I would like as the leaflet map displays the breaks I want however when I try adding them to the legend using the pal = I get an error

I have used the ClassInt package in R to find the jenks natural breaks in my data as follows:

[0,3]   (3,8]  (8,16] (16,32] (32,70] 
759     505     290     138      29

and then use findColours to and the RcolourBrewer package: 

cols_code <- findColours(cols_classes, brewer.pal(5,"YlGnBu"))

When I use this in my leaflet map it works fine and displays the colours thematically by polygon as I want:

leaflet() %>% 
addProviderTiles("CartoDB.Positron") %>%

 addPolygons(data = foo, 
          fillColor = cols_code, 
          fillOpacity = 0.9, 
          color = "white", 
          weight = 1)

But when I try to add a legend using this object I get an error:

addLegend(pal = cols_code, 
        values = foo$bar,
        title = "title",
        labFormat = labelFormat(suffix = " things"),
        opacity = 0.9)

Error in if (type == "numeric") { : argument is of length zero

I have tried using the leaflet colorBin and colorNumeric instead but they do not seem to recognize my breaks and instead overwrite into their own intervals in the legend and in the thematic.

Any suggestions welcome, I want to avoid converting them into a factor if possible as I can see that both findColours and colorBin functions have palettes attached to them but it only seems to look it up for the leaflet colorBins/numeric.

amonk
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MrMonkeyBum
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1 Answers1

2

Without a reproducible example it is not easy to know what exactly you want. But try:

pal2 <- leaflet::colorBin(palette = col.regions,
                          bins = length(at),
                          domain = at,
                          na.color = na.color)

where col.regions is a function to generate colors (e.g. some colorRampPalette or viridis), at are your breaks and na.color is some color for NA values.

Then you can do:

leaflet::addLegend(map = m,
                   pal = pal2,
                   opacity = 1,
                   values = at,
                   title = "someTitle")

We use this in mapview so that we can do:

mapview(breweries91, zcol = "founded", 
        at = seq(1400, 2300, 300), legend = TRUE)

You coud obviously use mapview which will handle this for you.

TimSalabim
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    Hi Tim, thanks for replying. I basically want my legend to be coloured and divided into the five natural break bins from my classIntervals() as above. This colours display in my leaflet map using the findColours object but I don't seem to be able to add this as a legend! When I try to add it as a legend I get that error. – MrMonkeyBum Jul 30 '16 at 19:11
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    When I try the colorBin `pal_volume<-colorBin(palette = "YlGnBu", domain = cols_classes$brks, bins =length(cols_classes$brks))` it seems to give me 7 bins instead of the five I want! – MrMonkeyBum Jul 30 '16 at 19:27
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    OK have figured it out I needed to add pretty = FALSE to the colorBin() function and the bin = the classInterval$brks so `pal_volume<-colorBin(palette = "YlGnBu", domain = cols_classes$brks, bins =cols_classes$brks, pretty = FALSE)`. Thanks again for responding! – MrMonkeyBum Jul 30 '16 at 20:17