在 R 中自动组合数据帧

Question

我开始创建我的数据框的两个子集，如下所示：

a = read_sf("a.shp")
a = st_make_valid(a)

#creating first subset with polygons from base year 2000
a1 = subset(a, year==2000)

#creating second subset with polygons from all the following years
a2 = subset(a, year>2000)

#creating buffer around base year
buffer = st_buffer(a1, 500)

#intersection of buffer from base year with polygons from the following years 
#(lets assume the column "year" in the data.frame has a range of years 2000-2010)
results2000 = st_intersection(buffer, a2)

我现在必须在 2010 年之前的每一年都执行这些步骤。所以接下来的结果将如下所示：

a = read_sf("a.shp")
a = st_make_valid(a)

#creating first subset with polygons from base year 2000
a1 = subset(a, year==2001)

#creating second subset with polygons from all the following years
a2 = subset(a, year>2001)

#creating buffer around base year
buffer = st_buffer(a1, 500)

#intersection of buffer from base year with polygons from the following years 
#(lets assume the column "year" in the data.frame has a range of years 2000-2010)
results2001 = st_intersection(buffer, a2)

唯一改变的条目是子集代码中的年份。

最后，我需要一个包含所有 10 个结果的 data.frame（结合 results2000 到 results2010，每个结果都将 2000 年到 2010 年之间的 10 年中的一年作为基准年）。

我可以创建所有 10 个结果并将它们组合起来

rbind(results2000,results2001,...) 

等等。

但是他们这样做是不是更简单？ 我想过使用foreach包中的foreach函数，可能是这样的

(Spatial) Efficient way of finding all points within X meters of a point?

但是使用 foreach 创建一个循环会导致绘制时间很长，因为 data.frame "a" 包含大约 100 万行。

谁能帮忙？

Answer 1

我不知道你用哪个包来获取数据，所以我会假设 st_intersection(buffer, a2) 的输出是一个数据框（因为你说你想要使用 rbind)。

如果是这样，您可以创建一个空列表（我在下面称为 outlist），然后在循环中填充该列表，最后将列表的不同元素 rbind 在一起。

见下面的代码：

a = read_sf("a.shp")
a = st_make_valid(a)


# Define your cutting year 
subset_yr <- 2000:2010
# Create an empty list you will populate
outlist <- vector(mode = "list", length = length(subset_yr))

# Your code in a loop
for(i in seq_along(subset_yr)) {
  #creating first subset with polygons from base year i (2000, 2001, etc.)
  a1 = subset(a, year==subset_yr[i])
  
  #creating second subset with polygons from all the following years
  a2 = subset(a, year>subset_yr[i])
  
  #creating buffer around base year
  buffer = st_buffer(a1, 500)
  
  #intersection of buffer from base year with polygons from the following years 
  outlist[[i]] = st_intersection(buffer, a2)
  
  #Add a column indicating the year
  outlist[[i]]$Year <- subset_yr[i]
}

# Bind everything together
rbind(outlist)