在绘制ggmap时在ggplot2中添加geom_text时出现问题

Question

我的问题与我们在ggplot中添加geom_text（）的时间有关，它给了我一个错误。我提到了以下链接，但无法解决我的问题。

访问过的问题：geom_text not working when ggmap and geom_point used

library(ggplot2)
library(maps)
library(Hmisc)
library(stringi)
data(state)
states <- map_data("state")
colnames(states)[5] <- "State"
states$State <- stri_trans_totitle(states$State)
df <- data.frame(state.x77,
              State = state.name,
              Abbrev = state.abb,
              Region = state.region,
              Division = state.division
)  

df2 <- merge(states,df,by="State")
df2 <- df2[order(df2$order),]
mid_range <- function(x) mean(range(x,na.rm=TRUE))
centres <- ddply(df2, .(Abbrev),
             colwise(mid_range,.(lat,long,Population)))

gg <- function(Cols) {
df2$Cols <- df2[,Cols]
ggplot(df2, aes(long,lat,fill=Cols))+
geom_polygon(aes(group=group)) 
#+ geom_text(aes(x=long,y=lat,label=Abbrev),data = centres,size=4)
}

使用上面的代码，我得到以下输出：

gg("Population")

然后，如果我取消注释geom_text（）函数并重新运行代码，我会收到以下错误：

Error in +geom_text(aes(x = long, y = lat, label = Abbrev), data = centres,  : 
invalid argument to unary operator

如果您选择回答，请简要说明发生此错误的原因。会很感激。

谢谢。

Answer 1

一个问题是使用geom_text行开头的+号。将+号移动到上一行的末尾。但仍然会产生错误。我认为问题在于两个数据框中的常见变量名称。将data和aes命令从ggplot移出geom_polygon。

library(ggplot2)
library(plyr)
library(maps)
library(Hmisc)
library(stringi)
data(state)
states <- map_data("state")
colnames(states)[5] <- "State"
states$State <- stri_trans_totitle(states$State)
df <- data.frame(state.x77,
              State = state.name,
              Abbrev = state.abb,
              Region = state.region,
              Division = state.division
)  

df2 <- merge(states,df,by="State")
df2 <- df2[order(df2$order),]
mid_range <- function(x) mean(range(x,na.rm=TRUE))
centres <- ddply(df2, .(Abbrev),
             colwise(mid_range,.(lat,long,Population)))


gg <- function(Cols) {
df2$Cols <- df2[,Cols]
ggplot()+                                                          # Changes made here
 geom_polygon(data = df2, aes(long,lat,fill=Cols,group=group)) +   # and here.
 geom_text(aes(x=long,y=lat,label=Abbrev), data = centres, size=4)
}

gg("Population")