在ggplot中添加符号作为标签

Question

我有一个 R 脚本，可以在美国地图上突出显示某些州。我想强调两个功能，而我在使用第二个功能时遇到了麻烦。我在下面附上了当前地图的样子。

如果他们的债券评级低于某个等级，则将整个州涂成红色（这有效）
如果评级在过去几年呈下降趋势，请在债券评级旁边给出红色向下箭头作为该州的标签。这些已经在下面的 df "dtrend" 中被标记和过滤。

非常感谢任何帮助。谢谢。

#cleanup
statedata <- read.csv(file = "statebondratingsmelted.csv", header = TRUE) 
head(statedata)
summary(statedata)

statedata <- subset(statedata, Year==2017)
statedata$Rank = as.numeric(levels(statedata$Rank))[statedata$Rank]
statedata$region <- tolower(statedata$region)
snames <- data.frame(region=tolower(state.name), long=state.center$x, lat=state.center$y)
snames <- merge(snames, statedata, by="region")
dtrend <- filter(mergestate, downwardtrendflag==1)
aaflag <- filter(mergestate, aa_flag==1)
us <- map_data("state")
mergestate <- merge(statedata, us, by="region")

library(ggplot2)
library(ggmap)

# Map Code
ggplot(color="black") +
    geom_map(data=us, map=us, aes(long, lat, map_id=region), fill="white", color = "#000000")+
    geom_map(data=dtrend, map=us, aes(fill="red", map_id=region), color ="#000000")+
    geom_map(data=aaflag, map=us, aes(fill="red", map_id=region), color ="#000000")+    
    geom_text(data=snames, aes(long, lat, label=Rating), size=3.0, color = "black")+
    coord_map()

这是当前输出：

statedata <- structure(list(region = c("alabama", "alaska", "arizona", "arkansas", 
"california", "colorado", "connecticut", "delaware", "florida", 
"georgia", "hawaii", "idaho", "illinois", "indiana", "iowa", 
"kansas", "kentucky", "louisiana", "maine", "maryland", "massachusetts", 
"michigan", "minnesota", "mississippi", "missouri", "montana", 
"nebraska", "nevada", "new hampshire", "new jersey", "new mexico", 
"new york", "north carolina", "north dakota", "ohio", "oklahoma", 
"oregon", "pennsylvania", "rhode island", "south carolina", "south dakota", 
"tennessee", "texas", "utah", "vermont", "virginia", "washington", 
"west virginia", "wisconsin", "wyoming"), Year = c(2017L, 2017L, 
2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 
2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 
2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 
2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 
2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 2017L, 
2017L, 2017L, 2017L), Rating = structure(c(4L, 4L, 4L, 4L, 5L, 
4L, 5L, 7L, 7L, 7L, 6L, 6L, 9L, 7L, 7L, 5L, 3L, 4L, 4L, 7L, 6L, 
5L, 6L, 4L, 7L, 4L, 7L, 4L, 4L, 2L, 6L, 6L, 7L, 6L, 6L, 6L, 6L, 
5L, 4L, 6L, 7L, 7L, 7L, 7L, 6L, 7L, 6L, 5L, 4L, 6L), .Label = c("A", 
"A-", "A+", "AA", "AA-", "AA+", "AAA", "BBB", "BBB-", "N/A"), class = "factor"), 
    Rank = c(3, 3, 3, 3, 4, 3, 4, 1, 1, 1, 2, 2, 10, 1, 1, 4, 
    5, 3, 3, 1, 2, 4, 2, 3, 1, 3, 1, 3, 3, 7, 2, 2, 1, 2, 2, 
    2, 2, 4, 3, 2, 1, 1, 1, 1, 2, 1, 2, 4, 3, 2), downwardtrendflag = structure(c(1L, 
    2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 2L, 
    1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 
    1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
    1L, 2L, 1L, 2L), .Label = c("0", "1", "FALSE"), class = "factor"), 
    aa_flag = c(0L, 0L, 0L, 0L, 1L, 0L, 1L, 0L, 0L, 0L, 0L, 0L, 
    1L, 0L, 0L, 1L, 1L, 0L, 0L, 0L, 0L, 1L, 0L, 0L, 0L, 0L, 0L, 
    0L, 0L, 1L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 1L, 0L, 0L, 0L, 0L, 
    0L, 0L, 0L, 0L, 0L, 1L, 0L, 0L)), .Names = c("region", "Year", 
"Rating", "Rank", "downwardtrendflag", "aa_flag"), row.names = c(NA, 
50L), class = "data.frame")

Answer 1

问题的关键部分是询问如何绘制刻度线。如果您对符号使用 unicode，则符号的行为就像 ggplot 中的文本，并且之前已在此处回答：Adding arrow symbols in ggplot text in R

你的问题有点复杂，因为你想用不同的颜色绘制箭头。因此，此脚本为箭头添加了另一层。

您的数据有一个列 downwardtrendflag 为 1 或 0。我已经使用它为使用 unicode“\u2193”的数据制作了标签。我更改了数据子集的方式，因为它有点混乱。

# Assign arrow to flagged states
library(plyr)
library(ggplot2)
library(ggmap)

us <- map_data("state")

# Format the data
statedata <- subset(statedata, Year==2017)
statedata$Rank = as.numeric(levels(statedata$Rank))[statedata$Rank]
statedata$region <- tolower(statedata$region)

snames <- data.frame(region=tolower(state.name), long=state.center$x, lat=state.center$y)
snames <- merge(snames, statedata, by="region")

# Find states which have either a downward trend or aa flag
highlight <- filter(mergestate, downwardtrendflag==1 | aa_flag==1)

# Create label for snames
snames$downwardtrendflag <- mapvalues(snames$downwardtrendflag, from = c(0,1), to = c("", '\u2193'))

为了绘制箭头，我不得不制作另一个几何图层，因为您希望颜色为红色。我使用参数 nudge_x 来偏移箭头。

# Map Code
ggplot(color="black") +
  geom_map(data=us, map=us, aes(long, lat, map_id=region), fill="white", color = "#000000") +
  geom_map(data=highlight, map=us, aes(map_id=region), fill="#F8766D", color ="#000000") +
  geom_text(data=snames, aes(long, lat, label=Rating), size=3.0, color = "black") +
  geom_text(data=snames, aes(long, lat, label=downwardtrendflag), size=3.0, color = "red", nudge_x = 2)+
  coord_map() +
  theme_nothing()

从视觉上看，这张地图并不美妙，因为两组标签存在冲突。您最好将评级绘制为等值线图，然后将箭头覆盖在有问题的状态上，如下所示：

# First we must order the levels in the factor
snames$Rating <- factor(snames$Rating, levels = rev(c("BBB-", "A-","A+","AA-","AA","AA+" ,"AAA")))

# Map Code
ggplot(color="black") +
  geom_map(data=snames, map=us, aes(map_id=region, fill = Rating), color = "#000000") +
  geom_map(data=highlight, map=us, aes(map_id=region), fill="#F8766D", color ="#000000") +
  geom_text(data=snames, aes(long, lat, label=downwardtrendlabel), size=3.0, color = "red")+
  scale_fill_brewer(palette = "Reds") +
  coord_map(ylim = c(25, 50)) + 
  labs(title = " US States Debt Rating", subtitle = " Arrows highlights states which have a dowward trend", caption = "Source: Add source of data") +
  theme_nothing(legend = TRUE)

在ggplot中添加符号作为标签

Adding symbol as a label in ggplot

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ggmap