use*_*361 6 memory io memory-management r matrix
假设我有一个巨大的m*n矩阵X(太大而无法读入内存)和二进制数字向量V的长度m.我的目标是读取X对应于V等于1(而不是对应于那些V[i] == 0)的行到专用data table/ matrix通过包(例如(但不一定相同)bigmemory或)的行ff.仅适用于对应的行V[i] == 1.
这可以通过黑客攻击来完成nrows,并skip在等read.table,但我在寻找一个bigmemory,ff等.由于RAM不足导致类型解决方案.
这是一个MWE,不能反映我的真实大小X.
X <- array(rnorm(100*5),dim=c(100,5))
write.csv(X,"target.csv")
V <- sample(c(rep(1,50),rep(0,50))) #Only want to read in half the rows corresponding to 1's
rm(X)
#Now ... How to read "target.csv"?
您如何使用命令行工具sed，构造一个命令来传递您想要在命令中读取的行。我不确定这是否会有一些命令长度限制......
# Check the data
head( X )
# [,1] [,2] [,3] [,4] [,5]
#[1,] 0.2588798 0.42229528 0.4469073 1.0684309 1.35519389
#[2,] 1.0267562 0.80299223 -0.2768111 -0.7017247 -0.06575137
#[3,] 1.0110365 -0.36998260 -0.8543176 1.6237827 -1.33320291
#[4,] 1.5968757 2.13831188 0.6978655 -0.5697239 -1.53799156
#[5,] 0.1284392 0.55596342 0.6919573 0.6558735 -1.69494827
#[6,] -0.2406540 -0.04807381 -1.1265165 -0.9917737 0.31186670
# Check V, note row 6 above should be skipped according to this....
head(V)
# [1] 1 1 1 1 1 0
# Get line numbers we want to read
head( which( V == 1 ) )
# [1] 1 2 3 4 5 7
# Read the first 5 lines where V == '1' in your example (remembering to include an extra line for the header row, hence the +1 in 'which()')
read.csv( pipe( paste0("sed -n '" , paste0( c( 1 , which( V == 1 )[1:6] + 1 ) , collapse = "p; " ) , "p' C:/Data/target.csv" , collapse = "" ) ) , head=TRUE)
# X V1 V2 V3 V4 V5
#1 1 0.2588798 0.4222953 0.4469073 1.0684309 1.35519389
#2 2 1.0267562 0.8029922 -0.2768111 -0.7017247 -0.06575137
#3 3 1.0110365 -0.3699826 -0.8543176 1.6237827 -1.33320291
#4 4 1.5968757 2.1383119 0.6978655 -0.5697239 -1.53799156
#5 5 0.1284392 0.5559634 0.6919573 0.6558735 -1.69494827
#6 7 0.6856038 0.1082029 0.1523561 -1.4147429 -0.64041290
我们实际传递给的命令sed是......
"sed -n '1p; 2p; 3p; 4p; 5p; 6p; 8p' C:/Data/target.csv"
我们用来-n关闭任何行的打印，然后使用分号分隔的行号向量来读取我们想要读取的行号，由 给定which( V == 1 )，最后是目标文件名。请记住，这些行号已被偏移，以+1说明构成标题行的行。