重复定义大量多边形栅格边界的六边形多边形过程

Question

抱歉。这是我第一次使用Whosebug，所以我不习惯发布问题。这是我正在编码的内容

library(raster)
library(landscapemetrics)
library(landscapetools)

# Add raster data for 2000
hex1_2000<-raster('2000_hex1.tif')
hex2_2000<-raster('2000_hex2.tif')
hex3_2000<-raster('2000_hex3.tif')
hex4_2000<-raster('2000_hex4.tif')
...
hex23_2000<-('2000_hex4.tif')

# Add raster data for 2010
hex1_2010<-raster('2010_hex1.tif')
hex2_2010<-raster('2010_hex2.tif')
hex3_2010<-raster('2010_hex3.tif')
hex4_2010<-raster('2010_hex4.tif')
...
hex23_2010<-('2000_hex4.tif')

#Create data frame as table

hex1 = data.frame(
  lc00 = values(hex1_2000),
  lc10 = values(hex1_2010))
hex2 = data.frame(
  lc00 = values(hex2_2000),
  lc10 = values(hex2_2010))
hex3 = data.frame(
  lc00 = values(hex3_2000),
  lc10 = values(hex3_2010))
hex4 = data.frame(
  lc00 = values(hex4_2000),
  lc10 = values(hex4_2010))
...
hex23 = data.frame(
  lc00 = values(hex23_2000),
  lc10 = values(hex23_2010))
...

hex1 = table(hex1[,c('lc00','lc10')])
hex2 = table(hex2[,c('lc00','lc10')])
hex3 = table(hex3[,c('lc00','lc10')])
hex4 = table(hex4[,c('lc00','lc10')])
...
hex23 = table(hex23[,c('lc00','lc10')])

#Define crosstabulation matrix

Hex1_Trans = as.matrix(hex1 / rowSums(hex1))
write.csv(Hex1_Trans, 'hex1Trans.csv')

Hex2_Trans = as.matrix(hex2 / rowSums(hex2))
write.csv(Hex2_Trans, 'hex2Trans.csv')

Hex3_Trans = as.matrix(hex3 / rowSums(hex3))
write.csv(Hex3_Trans, 'hex3Trans.csv')

Hex4_Trans = as.matrix(hex2 / rowSums(hex4))
write.csv(Hex4_Trans, 'hex2Trans.csv')

...
Hex23_Trans = as.matrix(hex23 / rowSums(hex23))
write.csv(Hex23_Trans, 'hex23Trans.csv')

如您所见，我在无数次重复相同过程的实例中。我很高兴知道如何使这段代码更简单、更优雅。我的编码总是这样，我发现这显然非常低效。感谢大家的帮助。

Answer 1

非常简单的解决方案，试试 assign()。此代码来自 Data Camp 的文档页面。

for(i in 1:6) { 
  #-- Create objects 'r.1', 'r.2', ... 'r.6' -- 
  nam <- paste("r", i, sep = ".") 
  assign(nam, 1:i) 
} 

ls(pattern = "^r..$")

这是页面的link。查看 'Examples' 部分。 rdocumentation.org/packages/base/versions/3.6.1/topics/assign

Answer 2

也许像下面这样的东西可以满足问题的要求。
这是重复使用 lapply 读取数据文件和 table 所需的列。

hexnames <- list.files(pattern = "2000_hex\d+\.tif")
hex_list <- lapply(hexnames, raster)
names(hex_list) <- paste0("hex", seq_along(hex_list), "_2000")
hex_table <- lapply(hex_list, function(X) table(X[, c('lc00','lc10')]))

Answer 3

这是一个不完整的草稿，说明了如何使用 Map 同时遍历 2000 年和 2010 年的数据。

fn_y2000 <- c("2000_hex1.tif", "2000_hex2.tif", "2000_hex3.tif")
fn_y2010 <- c("2010_hex1.tif", "2010_hex2.tif", "2010_hex3.tif")
lst <- Map(
    function(x1, x2) {
        hex1 <- raster(x1)
        hex2 <- raster(x2)
        tbl <- table(values(hex1), values(hex2))
        #... Normalise and write output 
    },
    fn_y2000, fn_y2010)

return 对象是 list。

重复定义大量多边形栅格边界的六边形多边形过程

Repeating a process of hexagon polygons that define raster boundaries for a large set of polygons

loops

r

repeat