如何使用ggplot绘制R中的降雨径流图? [英] How to draw rainfall runoff graph in R using ggplot?

问题描述

对于水文学家来说，通常使用降雨水文仪和水流水文仪.如下图所示.

For a hydrologist, the Rainfall Hyetograph and Streamflow Hydrograph is commonly used. It looks like the figure below.

X轴表示日期，左Y轴表示降雨量，右Y轴表示流量.

The X-axis represents Date and left Y-axis which is reversed represents rainfall and right Y-axis represents discharge.

我有一个降雨表和一个排水表.

I have a rainfall table and a discharge table.

  ####Rain Table####                   ####Discharge Table####
   Date         Value                     Date         Value
2000-01-01       13.2                   2000-01-01      150
2000-01-02       9.5                    2000-01-01      135
2000-01-03       7.3                    2000-01-01      58
2000-01-04       0.2                    2000-01-01      38

这是我的代码.

  ggplot(rain,aes(x=DATE,y=value)) + 
    geom_bar(stat = 'identity')+
    scale_y_reverse()+
    geom_line(data =discharge,aes(x=DATE,y=value))

但是我不知道如何在两个不同的Y轴上表示这些值.

But I don't know how to represent these value in two different Y-axis.

推荐答案

在ggplot中，可以使用sec_axis()函数显示第二根轴，这是第一根轴的变换.由于可以使用分水岭区域将降水量转换为一定体积(或将排放量转换为深度)，因此可以使用sec_axis制作hytograph.

It's possible in ggplot using the sec_axis() function to display a second axis that is a transformation of the first. Since precipitation can be transformed to a volume using watershed area (or discharge transformed into a depth), it's possible to use sec_axis to make a hyetograph.

library(ggplot2)
library(readr)

df <- read_csv("date, precip_in, discharge_cfs
                2000-01-01, 13.2, 150
                2000-01-02, 9.5, 135
                2000-01-03, 7.3, 58
                2000-01-04, 0.2, 38")

watershedArea_sqft <- 100

# Convert the precipitation to the same units as discharge. These steps will based on your units
df$precip_ft <- df$precip_in/12
df$precip_cuft <- df$precip_ft * watershedArea_sqft

# Calculate the range needed to avoid having your hyetograph and hydrograph overlap 
maxRange <- 1.1*(max(df$precip_cuft) + max(df$discharge_cfs))

# Create a function to backtransform the axis labels for precipitation
precip_labels <- function(x) {(x / watershedArea_sqft) * 12}

# Plot the data
ggplot(data = df,
       aes(x = date)) +
  # Use geom_tile to create the inverted hyetograph. geom_tile has a bug that displays a warning message for height and width, you can ignore it.
  geom_tile(aes(y = -1*(precip_cuft/2-maxRange), # y = the center point of each bar
                height = precip_cuft,
                width = 1),
            fill = "gray50",
            color = "white") +
  # Plot your discharge data
  geom_line(aes(y = discharge_cfs),
            color = "blue") +
  # Create a second axis with sec_axis() and format the labels to display the original precipitation units.
  scale_y_continuous(name = "Discharge (cfs)",
                     sec.axis = sec_axis(trans = ~-1*(.-maxRange),
                                         name = "Precipitation (in)",
                                         labels = precip_labels))

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