删除“0”序列之间的正值序列

Question

我想在数据框中创建一个小函数，用于检测（并设置为 0）位于等于 0 的值序列之间的正值序列，但前提是这些正值序列不超过长度超过 5 个值。

这里只是一个小例子，向您展示我的数据看起来如何（initial_data 列），以及我想在最后获得什么（final_data 列）：

DF<-data.frame(initial_data=c(0,0,0,0,100,2,85,0,0,0,0,0,0,3,455,24,10,7,6,15,42,0,0,0,0,0,0,0),final_data=c(0,0,0,0,0,0,0,0,0,0,0,0,0,3,455,24,10,7,6,15,42,0,0,0,0,0,0,0))

这句话也可以恢复诀窍： "如果有一个正值序列，不超过 5 个值，并且位于至少两个或三个 0 值之间（在这个正值序列之前和之后），那么也将该序列设置为 0"

有什么建议可以轻松做到这一点吗？

非常感谢！！！

Answer 1

这是使用rle 函数的可能方法：

DF<-data.frame(initial_data=c(0,0,0,0,100,2,85,0,0,0,0,0,0,3,455,24,10,7,6,15,42,0,0,0,0,0,0,0),
               final_data=c(0,0,0,0,0,0,0,0,0,0,0,0,0,3,455,24,10,7,6,15,42,0,0,0,0,0,0,0))

# using rle create an object with the sequences of consecutive elements 
# having the same sign (-1 means negative, 0 means zero, 1 means positive)
enc <- rle(sign(DF$initial_data))

# find the positive sequences having maximum 5 elements
posSequences <- which(enc$values == 1 & enc$lengths <= 5)

# remove index=1 or index=length(enc$values) if present because 
# they can't be surrounded by 0
posSequences <- posSequences[posSequences != 1 & 
                             posSequences != length(enc$values)]

# check if they're preceeded and followed by at least 2 zeros 
# (if not remove the index)
toForceToZero <- sapply(posSequences,FUN=function(idx){
                                           enc$values[idx-1]==0 &&
                                           enc$lengths[idx-1] >= 2 && 
                                           enc$values[idx+1] == 0 &&
                                           enc$lengths[idx+1] >= 2})
posSequences <- posSequences[toForceToZero]

# reverse the run-length encoding, setting NA where we want to force to zero
v <- enc$values
v[posSequences] <- NA

# create the final data vector by forcing NAs to 0  
final_data <- DF$initial_data
final_data[is.na(rep.int(v, enc$lengths))] <- 0

# check if is equal to your desired output
all(DF$final_data == final_data)

# > [1] TRUE

Answer 2

我最好的朋友rle 来救援：

notzero<-rle(as.logical(unlist(DF)))
Run Length Encoding
  lengths: int [1:7] 4 3 6 8 20 8 7
  values : logi [1:7] FALSE TRUE FALSE TRUE FALSE TRUE ...

现在只需找到values 为TRUE 和lengths values 替换为FALSE。然后调用inverse.rle 得到想要的输出。