R, ggplot2 - x 轴上的时间
原标题：R, ggplot2 - time on x axis
In R I have a data frame with bid and ask prices for a single day. Here is an example:
TimeHM; Bid_Price1; Ask_Price1
08:12; 101; 102
08:13; 101; 102
08:14; 102; 104
...
17:05; 104; 105
So, each new row is a new minute. Variable TimeHM is a character, while Bid_Price1 and Ask_Price1 are numeric.
I would like to plot Bid and ask prices for the whole day, and I would like to mark “10:00” with a vertical line. Here is my code:
ggplot(MyData, aes(x=TimeHM)) +
geom_line(aes(y=Bid_Price1, group=1)) +
geom_line(aes(y=Ask_Price1, group=1)) +
geom_vline(xintercept = "10:00", color="red", linetype="dashed") +
xlab("Time") + ylab("Price") + theme_classic(base_size = 20)
It works (also the vertical line), and “group=1” is also necessary for some reason. But the problem is that on the x-axis it labels each observation (for each minute). Instead I want to label some specific points in time, e.g. 9:00; 12:00; 15:00.
I have tried different solutions by googling. I guess the problem is that it does not see TimeHM as time. So, I tried the following before the ggplot:
MyData$TimeHM <- as.POSIXct(strptime(MyData$TimeHM, format="%H:%M"))
But then for some reason it adds the date of today, and then uses the time. For example, the first line suddenly becomes “07-25-2024 08:12:00”. Then I tried to add one of the following to the ggplot:
#scale_x_datetime(labels = date_format("%H:%M"))
#scale_x_date(labels = date_format("%H:%M"))
#scale_x_datetime(labels = label_date("%H:%M"))
It simply gives me an error. Somehow I once managed to plot it with scale_x_datetime, but both curves (bid and ask) were shifted to the left such that the first price was before 8:00 (while the dataset starts after 8:00). I have also tried with as_hms.
Can someone help? What is the right way to do it?
Thank you!
问题回答
Use dplyr s mutate to convert TimeHM to a datetime in a simple pipe, and scales::label_time to format the labels on scale_x_time():
library(ggplot2)
df <- data.frame(
TimeHM = c("08:12", "09:13", "10:14", "11:15"),
Bid_Price1 = c(100, 101, 102, 105),
Ask_Price1 = c(102, 103, 104, 106)
)
df |>
dplyr::mutate(TimeHM = as.POSIXct(TimeHM, format = "%H:%M", tz = "UTC")) |>
ggplot(aes(x = TimeHM)) +
geom_line(aes(y = Bid_Price1, group = 1), color = "#df2f9f") +
geom_line(aes(y = Ask_Price1, group = 1), color = "#106faf")+
geom_vline(xintercept = as.POSIXct("10:00", format = "%H:%M", tz = "UTC"), color = "red", linetype = "dashed")+
scale_y_continuous(limits = c(90, 110)) +
scale_x_time(
labels = scales::label_time(format = "%H:%M"),
breaks = as.POSIXct(c("09:00", "12:00", "15:00"), format = "%H:%M", tz = "UTC"),
limits = as.POSIXct(c("08:00", "15:59"), format = "%H:%M", tz = "UTC")
)
Coerce the time column to class "POSIXct" and scale_x_datetime will take care of the labels.
As for the two lines, it was asked before several times. This type of problems generally has to do with reshaping the data. The format should be the long format and the data is in wide format.
See this post on how to reshape the data from wide to long format.
And this post on how to separate the lines.
In the OP the aesthetic used is group, others (color, linetype) will further differentiate the lines and add a legend to the plot.
MyData <- read.csv2(text = "TimeHM; Bid_Price1; Ask_Price1
08:12; 101; 102
08:13; 101; 102
08:14; 102; 104
17:05; 104; 105")
suppressPackageStartupMessages({
library(dplyr)
library(ggplot2)
})
x0 <- as.POSIXct(paste(Sys.Date(), "10:00"))
MyData %>%
mutate(TimeHM = as.POSIXct(paste(Sys.Date(), TimeHM))) %>%
tidyr::pivot_longer(-TimeHM) %>%
ggplot(aes(TimeHM, value, group = name)) +
geom_line() +
geom_vline(xintercept = x0, color = "red", linetype = "dashed") +
scale_x_datetime(date_breaks = "3 hours", date_labels = "%H:%M") +
xlab("Time") +
ylab("Price") +
theme_classic(base_size = 20)
Created on 2024-07-25 with reprex v2.1.0
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