如何在 R 中将列从 "unknown" 转换为日期以使用 ggplot scale_x_date？

Question

我的数据帧中有一列显示为"；未知"；当我将光标悬停在列标题上时。它显示为以下打印的日期，带有head(dataframe)

示例数据：

date<date>  courses<int>  tasks<int>
1   2020-01-02  14      199
2   2020-01-03  14      246
3   2020-01-06  14      227
4   2020-01-07  14      83
5   2020-01-08  14      116
6   2020-01-09  14      178

我试过：

1. 将列格式化为"；日期"；导入前在excel中
2. 将导入设置更改为"；日期"；同时加载CSV和XLS文件时
3. 将数据导入为"；字符"；它们变为数字，然后变为日期。这确实提供了正确的格式；未知"；标题

我能够添加一周列，所以在某些情况下，数据似乎表现为日期，但在其他情况下则不然。

DFweek <- dataframe %>% mutate(Week = week(date))
head(DFweek)
date<date>  courses<int>  tasks<int>  <week><dbl>
1   2020-01-02  14      199 1
2   2020-01-03  14      246 1
3   2020-01-06  14      227 1
4   2020-01-07  14      83  1
5   2020-01-08  14      116 2
6   2020-01-09  14      178 2

该列始终显示为日期类型

> class(dataframe$date)
[1] "Date"
> str(dataframe$date)
Date[1:290], format: "2020-01-02" "2020-01-03" "2020-01-06" "2020-01-07" "2020-01-08" "2020-01-09" "2020-01-10" "2020-01-13" "2020-01-14"

此代码成功地制作了一个绘图

b <- diff(ylim.prim)/diff(ylim.sec)
a <- ylim.prim[1] - b*ylim.sec[1]
dataframeplot <- ggplot(dataframe, aes(date, courses)) +
geom_line() +
geom_bar(aes(y = a + tasks*b), color = "red", stat='identity') +
scale_y_continuous("Open Courses", sec.axis = sec_axis(~ (. - a)/b, name = "Tasks Completed")) +
scale_x_continuous("Month", breaks = 1:12) +
ggtitle("Title") +
theme(axis.line.y.right = element_line(color = "red"), 
axis.ticks.y.right = element_line(color = "red"),
axis.text.y.right = element_text(color = "red"), 
axis.title.y.right = element_text(color = "red")

) 
dataframeplot

我想使用scale_x_date，但下面的代码给了我一个错误

> dataframeplot2<- ggplot(dataframe, aes(date, courses)) +
+   geom_line() +
+   geom_bar(aes(y = a + tasks*b), color = "red", stat='identity') +
+   scale_y_continuous("Open Courses", sec.axis = sec_axis(~ (. - a)/b, name = "Tasks Completed")) +
+   scale_x_date("Month", breaks = 1:12) +
+   ggtitle("Title") +
+   theme(axis.line.y.right = element_line(color = "red"), 
+         axis.ticks.y.right = element_line(color = "red"),
+         axis.text.y.right = element_text(color = "red"), 
+         axis.title.y.right = element_text(color = "red")
+         
+         ) 
> dataframeplot2
Error: Invalid input: date_trans works with objects of class Date only

这是否意味着我的日期栏实际上不是日期格式？

Answer 1

您应该将scale_x_date("Month", breaks = 1:12)更改为scale_x_date(breaks = "1 month")。参见scale_x_date()的文档：https://www.rdocumentation.org/packages/ggplot2/versions/1.0.1/topics/scale_x_date