将表列表更改为R中的data.frame

Question

[下面，我首先查找变量X和Y是否具有重复少于4次的值。我在low中找到并列出了这些值。

我想知道，如何使用BASE R，将low列表中的table转换为如下所示的我想要的输出？

[[注：以下数据为玩具，感谢您提供实用的答案。

data <- data.frame(id = c(rep("AA",4), rep("BB",2), rep("CC",2)), X = c(1,1,1,1,1,1,3,3), 
                                                                  Y = c(9,9,9,7,6,6,6,6),
                                                                  Z = 1:8)
mods <- c("X","Y")
A <- setNames(lapply(seq_along(mods), function(i) table(data[[mods[i]]], dnn = NULL)), mods)

low <- setNames(lapply(seq_along(A), function(i) A[[i]][which(A[[i]] < 4)]), names(A))

所需的输出：

data.frame(id = c("CC", "AA", "AA"), value = c(3, 7, 9), var.name = c("X", "Y", "Y"), occur = c(2, 1, 3))

#   id value var.name occur     # `value` comes from the `names(low[[i]])`# i = 1,2                                 
# 1 CC     3        X     2     # `occur` comes from `as.numeric(low[[i]])`
# 2 AA     7        Y     1
# 3 AA     9        Y     3

Answer 1

我们用'id'拆分'data'的列子集，用list遍历lapply，用merge进行内部联接，并用stack ed'low'list table，Filter删除行数为0或length 0的元素以创建“ lst1”。在'lst1'中，使用names和Map元素从内部和外部rbind创建其他列

lst1 <- Filter(length, lapply(split(data[c('X', 'Y')], data$id), 
     function(dat) Filter(nrow, Map(merge, lapply(dat, 
        function(x) stack(table(x))), lapply(low, stack)))))

do.call(rbind, c(Map(cbind, id = names(lst1), lapply(lst1, 
   function(x) do.call(rbind, c(Map(cbind, x, var.name = names(x)),
          make.row.names = FALSE)))), make.row.names = FALSE))
#  id values ind var.name
#1 AA      1   7        Y
#2 AA      3   9        Y
#3 CC      2   3        X

Answer 2

data <- data.frame(id = c(rep("AA",4), rep("BB",2), rep("CC",2)), X = c(1,1,1,1,1,1,3,3), 
                   Y = c(9,9,9,7,6,6,6,6),
                   Z = 1:8)

to_check <- setdiff(names(data), "id")
results <- vector(mode = "list", length = length(to_check))

# This function sorts the input and then uses the run-length
# encoding to determining values and their frequencies.
# table is an option, but the output is a lot harder
# to work with.
count_occurrences <- function(x, max_occurrences = 3L) {
  x <- sort(x)
  run_lengths <- rle(x)
  chosen <- which(run_lengths$lengths <= max_occurrences)
  if (length(chosen)) {
    values <- run_lengths[["values"]][chosen]
    occur <- run_lengths[["lengths"]][chosen]
  } else {
    values <- NA
    occur <- NA
  }
  data.frame(value = values, occur = occur)
}
for (k in seq_along(results)) {
# `tapply` will split the first vector based upon the values in `INDEX`
counts <- tapply(data[[to_check[k]]], 
                 INDEX = data$id,
                 FUN = count_occurrences,
                 max_occurrences = 3)
# Construct a data.frame of the results, repeating each name for the number
# of rows (values meeting the criterion) returned. 
# I've used `unlist(sapply(...)` for the other two because
# not every result in the list will have the same number of rows,
# and `vapply()` requires specifying the output type and shape.
results[[k]] <- data.frame(id = rep(names(counts), times = vapply(counts, nrow, integer(1L))),
                           value = unlist(sapply(counts, `[[`, "value",
                                          USE.NAMES = FALSE), use.names = FALSE),
                           occur = unlist(sapply(counts, `[[`, "occur",
                                          USE.NAMES = FALSE), use.names = FALSE))
results[[k]]["var.name"] <- to_check[k]
}
desired_result <- Reduce(rbind, results)
desired_result
#    id value occur var.name
# 1  AA    NA    NA        X
# 2  BB     1     2        X
# 3  CC     3     2        X
# 4  AA     7     1        Y
# 5  AA     9     3        Y
# 6  BB     6     2        Y
# 7  CC     6     2        Y
# 8  AA     1     1        Z
# 9  AA     2     1        Z
# 10 AA     3     1        Z
# 11 AA     4     1        Z
# 12 BB     5     1        Z
# 13 BB     6     1        Z
# 14 CC     7     1        Z
# 15 CC     8     1        Z
# subset as [!is.na(value)] to drop the ids with no values with frequencies less
# than `max_occurrence`