如何在列表中保存100个SpatialLines对象?

问题描述

我需要在列表xySpatialLines中保存100个SpatialLines对象.下面给出的代码提供了一个错误:

I need to save 100 SpatialLines objects in the list xySpatialLines. The below given code provides an error:

library(sp)
xySpatialLines <- NULL

for(i in 1:100)
{
 x <- c(i,5,4,8)
 y <- c(1,3,4,i)
 xy <- cbind(x,y)
 xy.sp = sp::SpatialPoints(xy)
 spl <- SpatialLines(list(Lines(Line(xy.sp), ID=i)))
 xySpatialLines[i] = spl
}

推荐答案

初始化xySpatialLines不是作为NULL而是作为列表，例如由

Initialize xySpatialLines not as NULL but as a list, e.g. by

xySpatialLines <- list()

或者更好的是，预先分配避免增长所需的空间:

or better, pre-allocate the space you need to avoid incremental growth:

xySpatialLines <- vector(mode = "list", length = 100)

，然后执行其余脚本.

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