计算不同高度的横截面面积 [英] Calculate area of cross section for varying height

问题描述

我试图弄清楚如何计算河流横截面的面积.

I'm trying to figure out how to calculate the area of a river cross section.

对于横截面，我在5 m宽的河流上每25厘米处有一个深度.

For the cross section I have the depth at every 25 cm over the 5 m wide river.

x_profile <- seq(0, 500, 25)
y_profile = c(50, 73, 64, 59, 60, 64, 82, 78, 79, 76, 72, 68, 63, 65, 62, 61, 56, 50, 44, 39, 25)

如果有人对如何在r中完成此操作有任何建议，将非常感激.

If anyone have some suggestions of how this could be done in r it's highly appreciated.

推荐答案

我们可以使用sf包创建一个显示横截面的多边形，然后计算面积.请注意，要创建多边形，在创建矩阵m时，有必要再提供三个点，分别为c(0, 0)，c(500, 0)和c(0, 0).

We can use the sf package to create a polygon showing the cross-section and then calculate the area. Notice that to create a polygon, it is necessary to provide three more points as c(0, 0), c(500, 0), and c(0, 0) when creating the matrix m.

x_profile <- seq(0, 500, 25)
y_profile <- c(50, 73, 64, 59, 60, 64, 82, 78, 79, 76, 72, 
               68, 63, 65, 62, 61, 56, 50, 44, 39, 25)

library(sf)

# Create matrix with coordinates
m <- matrix(c(0, x_profile, 500, 0, 0, -y_profile, 0, 0),
            byrow = FALSE, ncol = 2)

# Create a polygon
poly <- st_polygon(list(m))

# View the polygon
plot(poly)

# Calcualte the area
st_area(poly)
31312.5

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