如何使用ggplot调整x轴上的时间？

Question

我正在尝试使用 ggplot 绘制（时间 VS 速度和降水），但我得到了一个混乱的图。数据在 (df) 下面，然后是我试过的代码。

    df <- structure(list(Agency.Station.ID = c("MI270N003.6D", "MI270N004.7D", 
"MI270N005.7D", "MI270N007.3D", "MI270N008.5D", "MI270N003.6D", 
"MI270N004.7D", "MI270N005.7D", "MI270N007.3D", "MI270N008.5D", 
"MI270N003.6D", "MI270N004.7D", "MI270N005.7D", "MI270N007.3D", 
"MI270N008.5D", "MI270N003.6D", "MI270N004.7D", "MI270N005.7D", 
"MI270N007.3D", "MI270N008.5D"), date_time = structure(c(1427846400, 
1427846400, 1427846400, 1427846400, 1427846400, 1427846700, 1427846700, 
1427846700, 1427846700, 1427846700, 1427847000, 1427847000, 1427847000, 
1427847000, 1427847000, 1427847300, 1427847300, 1427847300, 1427847300, 
1427847300), class = c("POSIXct", "POSIXt"), tzone = "UTC"), 
    Date = structure(c(16526, 16526, 16526, 16526, 16526, 16526, 
    16526, 16526, 16526, 16526, 16526, 16526, 16526, 16526, 16526, 
    16526, 16526, 16526, 16526, 16526), class = "Date"), Time = c("00:00:00", 
    "00:00:00", "00:00:00", "00:00:00", "00:00:00", "00:05:00", 
    "00:05:00", "00:05:00", "00:05:00", "00:05:00", "00:10:00", 
    "00:10:00", "00:10:00", "00:10:00", "00:10:00", "00:15:00", 
    "00:15:00", "00:15:00", "00:15:00", "00:15:00"), Speed = c(59, 
    34, 46, 61, 46, 58, 39, 51, 36, 52, 62, 47, 49, 57, 50, 59, 
    50, 35, 54, 44), Precipitation = c(0, 0, 0, 0, 0, 0, 0, 0, 
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)), row.names = c(NA, 20L
), class = "data.frame")

这是我试过的代码：

df <- df %>% gather(Aspect, Value, -Agency.Station.ID, -Date, -Time)
df$Agency.Station.ID <- factor(df$Agency.Station.ID)
df$Date <- factor(df$Date)
for(i in levels(df$Agency.Station.ID)) {
  pdf(paste0(i,'.pdf'))

  for(j in levels(df$Date)) {
    subset.data <- df[which(df$Agency.Station.ID==i & df$Date==j),]
    if (nrow(subset.data)!=0) {
      p <- ggplot(data=subset.data, aes(Time, Value, group = 1)) +
        geom_line(aes(color=Aspect)) +
        labs(title=paste('Station:',i, " Date:",j)) +
        theme_bw()
      invisible(print(p))
    }
  }
  dev.off()
}

我担心的是时间（我有 288 observations/day），因为它将在 x 轴上被压缩。

Answer 1

不是将 Date Time 存储在单独的列中，而是可以组合：

df$Datetime <- as.POSIXct(paste0(df$Date, df$Time))

现在 ggplot 打印 x 轴上的所有标签，因为 Time 给出为 character。 ggplot 调用函数以 prettify 轴标签，即打印信息性的、不重叠的标签。这需要 numeric 变量的变体，例如 R 的日期时间表示 POSIXct.

PS：你的例子对我不起作用，缺少 Aspect。

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