R传单连续图例中的相反顺序 [英] reverse order in R leaflet continuous legend

问题描述

我正在尝试在 R 中反转我的 leaflet 图例的值显示.这个

但是，如果您一直使用 pal() 函数在地图上绘制任何内容，那么您现在完全错了.

# 但是100是蓝色的，不是红色的图(1、1、pch = 19、cex = 3、col = pal(100))

我认为解决方案是定义为数字分配颜色的函数，一个用于图例，一个用于实际绘图:

pal_rev <- colorNumeric(c("#d7191c","#fdae61","#ffffbf","#abd9e9", "#2c7bb6"), x, reverse = TRUE)地图 %>% addLegend('topright',pal = pal_rev,值 = x，labFormat = labelFormat(transform = function(x) sort(x, reduction = TRUE)))

这为我们提供了一个与我们将绘制的任何内容相匹配的图例，即 100 现在正确地显示为蓝色:

I am trying to reverse the value display of my leaflet legend in R. This post covers categorical data, but I am working with continuous data. Here's a toy example:

map <- leaflet() %>% addProviderTiles('Esri.WorldTopoMap')
x <- 1:100
pal <- colorNumeric(c("#d7191c","#fdae61","#ffffbf","#abd9e9", "#2c7bb6"), x)
map %>% addLegend('topright', pal=pal, values=x)

I'd like the legend to read 100 at the top and 1 on the bottom with the colors reversed. I can certainly reverse the colors in colorNumeric(), but reversing the order of the labels is harder. I have tried reversing the order of the values in x, and I even fiddled with the labelFormat() parameter for addLegend() to reference a lookup table of reversed values... nothing seems to work. Is there an easy way to do this?

解决方案

Unfortunately the accepted answer to this will get the numbers out of alignment (in fact exactly reversed) from the colours they represent.

Here's the original proposed solution, which I say is incorrect:

map <- leaflet() %>% addProviderTiles('Esri.WorldTopoMap')
x <- 1:100
pal <- colorNumeric(c("#d7191c","#fdae61","#ffffbf","#abd9e9", "#2c7bb6"), x)
map %>% addLegend('topright', pal=pal, values=x)

# This solution shows 100 as red
map %>% addLegend('topright',
                  pal = pal, 
                  values = x, 
                  labFormat = labelFormat(transform = function(x) sort(x, decreasing = TRUE)))

But if you've been using the pal() function to draw anything on your map, you now have it exactly wrong.

# But 100 is blue, not red
plot(1, 1, pch = 19, cex = 3, col = pal(100))

I think the solution is to define to functions that allocate colours to numbers, one in reverse for the legend, and one for actually drawing things:

pal_rev <- colorNumeric(c("#d7191c","#fdae61","#ffffbf","#abd9e9", "#2c7bb6"), x, reverse = TRUE)

map %>% addLegend('topright',
                  pal = pal_rev, 
                  values = x, 
                  labFormat = labelFormat(transform = function(x) sort(x, decreasing = TRUE)))

This gives us a legend that matches anything we will have drawn ie 100 is now correctly shown to be blue:

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