从R中的二进制矩阵中提取子矩阵

Question

说二进制矩阵m:

      # [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
 # [1,]    0    0    0    0    0    0    0    0    0
 # [2,]    0    0    0    0    0    0    0    0    0
 # [3,]    0    0    0    1    1    1    1    0    0
 # [4,]    0    0    0    1    1    1    1    0    0
 # [5,]    0    0    0    1    1    1    1    0    0
 # [6,]    0    0    0    0    0    0    0    0    0
 # [7,]    0    1    1    0    0    0    0    1    1
 # [8,]    0    1    1    0    1    1    0    1    1
 # [9,]    0    0    0    0    1    1    0    1    1
# [10,]    0    0    0    0    1    1    0    0    0

m <- structure(c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 
1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 
0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 1, 1, 
1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 
0, 0, 0, 0, 0, 0, 1, 1, 1, 0), .Dim = c(10L, 9L))

我们如何提取那些被1评估的子矩阵？例如

m[7:9,8:9]

#     [,1] [,2]
#[1,]    1    1
#[2,]    1    1
#[3,]    1    1

关键是我想在算法上提取它们而不是明确地将它们编入索引m[7:9,8:9].

• 输入是二进制矩阵
• 子矩阵作为输出的列表(的暗淡的四个矩阵如此列表3*4,2*2,3*2和3*2)
• 子矩阵的1值是矩形的
• 子矩阵的边界用零保护.

Answer 1

我将它视为一个空间问题,你有一个光栅,并想要检测连接单元格的区域.

library(raster)
r <- raster(m)

library(igraph)
rc <- clump(r)

plot(rc, col = rainbow(rc@data@max))

m1 <- as.matrix(rc)

lapply(seq_len(rc@data@max), function(x) {
  inds <- which(m1 == x, arr.ind = TRUE)
  nrow <- diff(range(inds[, "row"])) + 1
  ncol <- diff(range(inds[, "col"])) + 1
  matrix(1, ncol = ncol, nrow = nrow)
})
#[[1]]
#     [,1] [,2] [,3] [,4]
#[1,]    1    1    1    1
#[2,]    1    1    1    1
#[3,]    1    1    1    1
#
#[[2]]
#     [,1] [,2]
#[1,]    1    1
#[2,]    1    1
#
#[[3]]
#     [,1] [,2]
#[1,]    1    1
#[2,]    1    1
#[3,]    1    1
#
#[[4]]
#     [,1] [,2]
#[1,]    1    1
#[2,]    1    1
#[3,]    1    1