如何在 r 中缩放 ggplot2 中 x 轴的时间（小时）？答案

【问题标题】：How can I scale the time (hours) of my x-axis in ggplot2 in r?如何在 r 中缩放 ggplot2 中 x 轴的时间（小时）？
【发布时间】：2018-08-12 18:39:58
【问题描述】：

我用 ggplot2 创建了一个 ggplot。该图是一年的时间序列测量，我已经组织了几个月。这是我的代码：

ggplot(data = mydataframe, aes(x = time)) +
  geom_point(aes(y = H_flux_6262_R3,  color = "6262-R3"),
             alpha = 0.5,
             shape = 19) +
  geom_point(aes(y = H_flux_7200_HS,  color = "7200-HS"),
             alpha = 0.5,
             shape = 5) +
  geom_point(
    aes(y = H_flux_dif_6262_R3_7200_HS,  color = "Difference"),
    alpha = 0.5,
    shape = 5
  ) +
  facet_wrap( ~ Month, nrow = 3) +
  theme(text = element_text(),
        axis.text.x = element_text(angle = 60, hjust = 1)) +
  theme(legend.position = "right", legend.title = element_blank()) +
  scale_color_manual(values = c("#56B4E9", "#E69F00", "palegreen4")) +
  labs(x = "time", y = "H flux")

我的时间格式是：%H:%M:%S，比如00:00:00。

H flux 6262_R3 H_flux_7200_HS Time
 100             500         02:00:00
 400             700         02:30:00
 400             700         03:00:00
 400             700         03:30:00
 400             700         04:00:00
 100             500         04:30:00
 400             700         05:00:00
 400             700         05:30:00
 400             700         06:30:00
 400             700         07:00:00

以此类推，直到 00:00:00。我每 30 分钟测量一次我的数据。当我绘图时，我遇到的问题是它不会将其缩放到例如每 4 小时一次，因为我不需要它们，所以没有秒数。我已经用很多不同的方法尝试过它，它就是行不通。我现在很绝望，对不起。 Mabye有人可以帮助我吗？我会很感激的！

【问题讨论】：

ggplot2.tidyverse.org/reference/scale_date.html
谢谢！我也用那个代码试过了，但它仍然不起作用。对不起，你能不能给我更多的线索？
请分享您的数据，以便其他人可以提供帮助。在此处查看更多信息How to make a great R reproducible example?
完成！感谢您的评论！
dput(mydataframe) 会更好。如果太长，请尝试dput(head(mydataframe, 50))

标签： r ggplot2 time scaling

【解决方案1】：

你快到了。您可以稍微修改代码以获得所需的输出。需要修改的是：

1.Convert `Time` column to `POSIXct` type
2.The `facet_wrap` should use month part of `Time` column. Hence it can be written as:
          facet_wrap(~format(Time,"%m"), scales = "free")
3.Use of `scale_x_datetime` to format x-axis to write label every 4 hours can be as:
          scale_x_datetime(date_breaks = "4 hours", date_labels = "%Y-%m-%d %H:%M")

解决办法：

#First prepare the data to have Time column of type POSIXct and diff column
mydataframe$Time = as.POSIXct(mydataframe$Time, format = "%m-%d-%Y %H:%M:%S")
mydataframe$H_flux_dif_6262_R3_7200_HS <- mydataframe$H_flux_7200_HS -
                                                   mydataframe$H_flux_6262_R3


library(ggplot2)
ggplot(data = mydataframe, aes(x = Time)) +
  geom_point(aes(y = H_flux_6262_R3,  color = "6262-R3"),
             alpha = 0.5,
             shape = 19) +
  geom_point(aes(y = H_flux_7200_HS,  color = "7200-HS"),
             alpha = 0.5,
             shape = 5) +
  geom_point(
    aes(y = H_flux_dif_6262_R3_7200_HS,  color = "Difference"),
    alpha = 0.5,
    shape = 5
  ) +
  facet_wrap(~format(Time,"%m"), scales = "free") +
  scale_x_datetime(date_breaks = "4 hours", date_labels = "%Y-%m-%d %H:%M")+
  theme(text = element_text(),
        axis.text.x = element_text(angle = 60, hjust = 1)) +
  theme(legend.position = "right", legend.title = element_blank()) +
  scale_color_manual(values = c("#56B4E9", "#E69F00", "palegreen4")) +
  labs(x = "time", y = "H flux")

输出：

数据：数据与OP提供的数据类似。我已将其延长至 2 个月。此外，要包括 Date 部分时间。

mydataframe <- read.table(text = 
"H_flux_6262_R3 H_flux_7200_HS Time
100             500         '01-01-2018 02:00:00'
400             700         '01-01-2018 02:30:00'
400             700         '01-01-2018 03:00:00'
400             700         '01-01-2018 03:30:00'
400             700         '01-01-2018 04:00:00'
100             500         '01-01-2018 04:30:00'
400             700         '01-01-2018 05:00:00'
400             700         '01-01-2018 05:30:00'
400             700         '01-01-2018 06:00:00'
400             700         '01-01-2018 06:30:00'
400             700         '01-01-2018 07:00:00'
400             700         '01-01-2018 07:30:00'
400             700         '01-01-2018 08:00:00'
400             700         '01-01-2018 08:30:00'
400             700         '01-01-2018 09:00:00'
400             700         '01-01-2018 09:30:00'
400             700         '01-01-2018 10:00:00'
400             700         '01-01-2018 10:30:00'
400             700         '01-01-2018 11:00:00'
500             900         '01-01-2018 11:30:00'
500             900         '01-01-2018 12:00:00'
100             500         '02-01-2018 02:00:00'
400             700         '02-01-2018 02:30:00'
400             700         '02-01-2018 03:00:00'
400             700         '02-01-2018 03:30:00'
400             700         '02-01-2018 04:00:00'
100             500         '02-01-2018 04:30:00'
400             700         '02-01-2018 05:00:00'
400             700         '02-01-2018 05:30:00'
400             700         '02-01-2018 06:00:00'
400             700         '02-01-2018 06:30:00'
400             700         '02-01-2018 07:00:00'
400             700         '02-01-2018 07:30:00'
400             700         '02-01-2018 08:00:00'
400             700         '02-01-2018 08:30:00'
400             700         '02-01-2018 09:00:00'
400             700         '02-01-2018 09:30:00'
400             700         '02-01-2018 10:00:00'
400             700         '02-01-2018 10:30:00'
400             700         '02-01-2018 11:00:00'
500             900         '02-01-2018 11:30:00'
500             900         '02-01-2018 12:00:00'",
header = TRUE, stringsAsFactors = FALSE)

【讨论】：

非常感谢！它有效，我很抱歉现在回复！现在我知道如何将时间转换为 posixct 并缩放我的坐标轴，这真的很有帮助！