如何使用R绘制带有自定义标题的两列时间序列网格？

install.packages("ggplot2")
install.packages("gridExtra")
library(ggplot2)
library(gridExtra)

df1 <- data.frame(Date = seq(as.Date("2022-01-01"), as.Date("2022-01-31"), by = "day"),
                  Value = runif(31, min = 0, max = 100))

df2 <- data.frame(Date = seq(as.Date("2022-02-01"), as.Date("2022-02-28"), by = "day"),
                  Value = runif(28, min = 0, max = 100))

# 创建第一个时间序列网格图
plot1 <- ggplot(df1, aes(x = Date, y = Value)) +
         geom_line() +
         labs(title = "第一个时间序列网格图", x = "日期", y = "值")

# 创建第二个时间序列网格图
plot2 <- ggplot(df2, aes(x = Date, y = Value)) +
         geom_line() +
         labs(title = "第二个时间序列网格图", x = "日期", y = "值")

# 合并两个网格图
grid.arrange(plot1, plot2, ncol = 2, top = "自定义标题的两列时间序列网格")