在ggplot2中的geom_line上绘制geom_point，并使用由值范围定义的点的颜色

Question

我正在尝试在 geom_line 上绘制 geom_point 并根据一系列值（值阈值为 0-8.3 和 8.4-946）对点进行颜色编码。 我已经尝试根据 ggplot geom_point() 使用基于特定离散值的颜色对点进行颜色编码，但图例上仅显示一种颜色（绿色）和一个阈值。我可以看到一些绿点，但看不到红点。 该图也仅显示 1 月份的数据，但时间序列是从 1 月到 8 月。

# Load libraries
library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
library(ggplot2)
library(scales)

# Define start and end times
start_time <- as.POSIXct("2024-01-01 00:00:00")
end_time <- as.POSIXct("2024-08-31 23:59:59")

# Generate a sequence of 15-minute intervals 
time_sequence <- seq(start_time, end_time, by = "15 mins")

# 1455 timestamps to match the number of observations 
time_sequence <- time_sequence[1:1455]

# Create a "Value" variable 
set.seed(123)  # For reproducibility
Value <- runif(1455, min = 2.3, max = 946)

# Generate the "Flow" variable 
t <- 1:1455  # Sequence representing each time point
Flow <- 5.2 + 4.2 * sin(2 * pi * t / 365)

# Create the data frame
data <- data.frame(
  Timestamp = time_sequence,
  Value = Value,
  Flow = Flow
)

# Create a duplicate data frame for the "Flow" variable
flow_duplicate <- data %>%
  select(Timestamp, Flow)  # Keep only Timestamp and Flow columns

# Display the first few rows of both data frames
head(data)
#>             Timestamp     Value     Flow
#> 1 2024-01-01 00:00:00 273.68691 5.272296
#> 2 2024-01-01 00:15:00 746.22356 5.344571
#> 3 2024-01-01 00:30:00 388.25152 5.416803
#> 4 2024-01-01 00:45:00 835.60352 5.488970
#> 5 2024-01-01 01:00:00 889.81898 5.561052
#> 6 2024-01-01 01:15:00  45.29167 5.633027
head(flow_duplicate)
#>             Timestamp     Flow
#> 1 2024-01-01 00:00:00 5.272296
#> 2 2024-01-01 00:15:00 5.344571
#> 3 2024-01-01 00:30:00 5.416803
#> 4 2024-01-01 00:45:00 5.488970
#> 5 2024-01-01 01:00:00 5.561052
#> 6 2024-01-01 01:15:00 5.633027



# plot the values as geom-point on the flow geom_line
ggplot(data = flow_duplicate, aes(Timestamp, Flow)) +
  geom_line() +  # plot the flow
  geom_point(data = data, aes(Timestamp, Flow, colour = cut(Value, c(0, 8.3, 946))),
             size = 1) +
  scale_color_manual(name = "Value",
                     values = c("(0,8.3]" = "green",
                                "(8.3, 945.8]" = "red"),
                     labels = c("<value threshold (8.3 NTU)", ">value threshold (8.3 NTU)"))+
  scale_y_continuous(labels = comma, name = 'Flow (cubic meters/d)') +
  theme_bw() 

Created on 2024-11-05 with reprex v2.1.0

Answer 1

正如我在评论中提到的，使用

"(8.3,946]" = "red"

应该可以解决红点问题：

library(dplyr, warn=FALSE)
library(ggplot2)
library(scales)

# Define start and end times
start_time <- as.POSIXct("2024-01-01 00:00:00")
end_time <- as.POSIXct("2024-08-31 23:59:59")

# Generate a sequence of 15-minute intervals
time_sequence <- seq(start_time, end_time, by = "15 mins")

# 1455 timestamps to match the number of observations
time_sequence <- time_sequence[1:1455]

# Create a "Value" variable
set.seed(123) # For reproducibility
Value <- runif(1455, min = 2.3, max = 946)

# Generate the "Flow" variable
t <- 1:1455 # Sequence representing each time point
Flow <- 5.2 + 4.2 * sin(2 * pi * t / 365)

# Create the data frame
data <- data.frame(
  Timestamp = time_sequence,
  Value = Value,
  Flow = Flow
)

# Create a duplicate data frame for the "Flow" variable
flow_duplicate <- data %>%
  select(Timestamp, Flow) # Keep only Timestamp and Flow columns

# plot the values as geom-point on the flow geom_line
ggplot(data = flow_duplicate, aes(Timestamp, Flow)) +
  geom_line() + # plot the flow
  geom_point(
    data = data, aes(Timestamp, Flow, colour = cut(Value, c(0, 8.3, 946))),
    size = 1
  ) +
  scale_color_manual(
    name = "Value",
    values = c(
      "(0,8.3]" = "green",
      "(8.3,946]" = "red"
    ),
    labels = c("<value threshold (8.3 NTU)", ">value threshold (8.3 NTU)")
  ) +
  scale_y_continuous(labels = comma, name = "Flow (cubic meters/d)") +
  theme_bw()