多个图形的使用:打印绘图中的错误

Question

在回答这个问题时：

比较巴尔的摩市机动车排放源和加州洛杉矶县机动车排放源的排放量(fips == "06037")。哪个城市的机动车排放量随着时间的推移发生了更大的变化？

我能够回答这个查询，但无法使用ggplot创建传奇：

#load library
library(data.table)
library(ggplot2)

#import rds files
NEI <- readRDS("summarySCC_PM25.rds")
SCC <- readRDS("Source_Classification_Code.rds")

#convert to data tables
NEI.DT <- data.table(NEI)
SCC.DT <- data.table(SCC)

#Get data for Baltimore
NEI.DT.Baltimore <- NEI.DT[fips=="24510", ]
NEI.DT.LA <- NEI.DT[fips=="06037", ]

#Check for Motor & Vehicle in SCC data using EI.Sector
motorVehicelSrcs <- SCC.DT[grep("[Mm]obile | [Vv]ehicles",  EI.Sector),   SCC]
emissionsBaltimore <- NEI.DT.Baltimore[SCC %in% motorVehicelSrcs,    sum(Emissions), by="year"]
emissionsLA <- NEI.DT.LA[SCC %in% motorVehicelSrcs, sum(Emissions), by="year"]

View(emissionsBaltimore)
View(emissionsLA)

setnames(emissionsBaltimore , "V1" , "Emissions") 
setnames(emissionsLA , "V1" , "Emissions") 

#plot data
plot_x <- ggplot(emissionsBaltimore, aes(year, Emissions)) +     geom_line(aes(data=emissionsBaltimore, x=year, y= Emissions, colour = "MyLine1")) + geom_point(colour = "blue") + geom_line(aes(data = emissionsLA, x= year, y= Emissions, colour = "MyLine2")) + geom_point(data= emissionsLA, colour = "black") + scale_colour_manual(name="Line Color", values=c(MyLine1="green", MyLine2="red"))
print(plot_x)

我得到了以下错误：

Error: "Don't know how to automatically pick scale for object of type data.table/data.frame. Defaulting to continuous
Error: Aesthetics must either be length one, or the same length as the dataProblems:emissionsBaltimore"

有人能帮忙解决错误吗？

以上代码的数据可在以下站点获得：data.zip

Answer 1

这一改变应能奏效：

plot_x <- ggplot(NULL, aes(year, Emissions)) +
          geom_line(data = emissionsBaltimore, colour = "green") + 
          geom_point(data = emissionsBaltimore, colour = "blue") + 
          geom_line(data = emissionsLA, colour = "red") + 
          geom_point(data = emissionsLA, colour = "black")
print(plot_x)

编辑：如果需要包含一个图例，那么将数据集分解成一个更简单：

library(reshape2)
emissionsAll <- melt(list(BA=emissionsBaltimore, LA=emissionsLA), id.vars="year")

plot_x2 <- ggplot(emissionsAll, aes(year, value, group=L1, color=L1)) + 
           geom_line() + 
           geom_point()
print(plot_x2)

Answer 2

您可以通过修改数据帧来实现它。

x <- cbind(emissionsBaltimore, emissionsLA$Emissions)
colnames(x) <- c("year", "Baltimore", "LA")
y <- x %>% gather(City, Emissions, -year)

(您需要使用'gathe'r函数的"tidyr“包)

ggplot(y, aes(x=year, y=Emissions, group=City))+
    geom_point()+
    geom_line(aes(colour=City))+
    scale_colour_manual(name="Line Color", values=c("green", "red"))

否则，使用“多重图”函数