在运行2个绘图命令后调用Par（NEW = True），没有绘图

Question

library(bigrquery)
install.packages('readr')
project <- "grab-analysis" # put your project ID here
taxiQuery <- "SELECT ROUND(pickup_latitude, 4) as lat,
                ROUND(pickup_longitude, 4) as long, COUNT(*) as
num_pickups FROM `bigquery-public-data.new_york.tlc_yellow_trips_2016` WHERE
(pickup_latitude BETWEEN 40.61 AND 40.91) AND
(pickup_longitude BETWEEN -74.06 AND -73.77 ) GROUP
BY lat, long"
taxiQuery1 <- "SELECT ROUND(pickup_latitude, 4) as lat,
                ROUND(pickup_longitude, 4) as long, COUNT(*) as
num_pickups FROM `bigquery-public-data.new_york.tlc_green_trips_2016` WHERE
(pickup_latitude BETWEEN 40.61 AND 40.91) AND
(pickup_longitude BETWEEN -74.06 AND -73.77 ) GROUP
BY lat, long"    

taxi_df <- query_exec(taxiQuery, project = project, max_pages = Inf,use_legacy_sql = FALSE)
taxi_df1 <- query_exec(taxiQuery1, project = project, max_pages = Inf,use_legacy_sql = FALSE)
require(ggplot2)

taxi_plot <- ggplot(data=taxi_df, aes(x = long, y = lat))
    taxi_plot1 <- ggplot(data=taxi_df1, aes(x=long,y=lat))
    final_plot = taxi_plot + geom_point(aes(alpha = as.factor(num_pickups)),size=0.4, color="white") + 
    scale_alpha_discrete(range = c(0.1,1), guide = FALSE) +
      theme(panel.background = element_rect(fill="black", color="black"),
            panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
            axis.text = element_blank(), axis.line = element_blank(),
            axis.title = element_blank(), axis.ticks = element_blank(),
            panel.border = element_blank(),
            plot.background = element_rect(fill="black", color="black"))
    plot(taxi_plot1 + geom_point(aes(alpha = as.factor(num_pickups)),
                            size=0.4, color="green") +scale_alpha_discrete(range = c(0.1,1), guide = FALSE))

我试图在taxi_df和taxi_df1代表的同一地块上绘制两种出租车的出租车接送点。但是，在使用par（new = TRUE）之后，我收到错误消息par(new = TRUE) : calling par(new=TRUE) with no plot。

我似乎无法弄清楚问题。