返回连续值满足条件的行 [英] Return rows where consecutive values meet criterion
问题描述
我有以下数据框 df
。我想返回一个向量 result
,该向量指示哪些行满足以下条件:该行中至少有2个连续值小于-1.7。
I have the following dataframe df
. I would like to return a vector result
that indicates which rows meet the following criterion: at least 2 consecutive values in that row are lower than -1.7.
set.seed(123)
df <- data.frame(V1=rnorm(10,-1.5,.5),
V2=rnorm(10,-1.5,.5),
V3=rnorm(10,-1.5,.5),
V4=rnorm(10,-1.5,.5),
V5=rnorm(10,-1.5,.5),
V6=rnorm(10,-1.5,.5),
V7=rnorm(10,-1.5,.5),
V8=rnorm(10,-1.5,.5),
V9=rnorm(10,-1.5,.5),
V10=rnorm(10,-1.5,.5))
rownames(df) <- c(seq(1976,1985,1))
结果将是一个向量:
result <- c(1977,1979,1980,1982,1983,1985)
推荐答案
一种选择是循环通过使用 apply
的行,使用 rle
,检查是否有任何
个具有个长度
的TRUE元素大于1,提取名称
One option is to loop through the rows with apply
, create a logical condition with rle
, check if there are any
TRUE elements that have lengths
more than 1, extract the names
names(which(apply(df, 1, function(x) with(rle(x < - 1.7), any(lengths[values] > 1)))))
#[1] "1977" "1979" "1980" "1982" "1983" "1985"
更好的方法是通过放置两个逻辑矩阵(即删除数据集的第一列,检查它是否小于-1.7,类似地删除最后一列并执行相同的操作), Reduce
使其成为单个逻辑<$ c $通过检查相应元素是否为 TRUE
c> matrix ,获取 rowSums
,如果值大于0,我们提取行名称
Or a better approach is to vectorize it by placing two logical matrices (i.e. remove the first column of the dataset, check whether it is less than -1.7, similarly remove the last column and do the same), Reduce
it to a single logical matrix
by checking whether the corresponding elements are TRUE
, get the rowSums
, if the value is greater than 0, we extract the row names
names(which(rowSums(Reduce(`&`, list(df[-ncol(df)] < -1.7, df[-1] < -1.7))) > 0))
#[1] "1977" "1979" "1980" "1982" "1983" "1985"
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