R 如何从列表中筛选所有季度时间序列？

我有一个列表，包含几个不同长度和频率的时间序列。类似于此：

library(tstools)

list <- list(ts(runif(200), end =  c(2021,1), frequency = 12),
             ts(runif(150), end =  c(2021,1), frequency = 12),
             ts(runif(75), end =  c(2021,1), frequency = 4),
             ts(runif(100), end =  c(2021,1), frequency = 12),
             ts(runif(25), end =  c(2021,1), frequency = 4),
             ts(runif(100), end =  c(2021,1), frequency = 12)
             )

库（tstools）
列出其中任何一项都将提取季度序列。没有使用任何软件包

Filter(function(x) frequency(x) == 4, list)

或

freq其中任何一个都将提取季度序列。没有使用任何软件包

Filter(function(x) frequency(x) == 4, list)

或

freq
s <- split(list, freq)  # freq defined above
s[["4"]]

L <- lapply(s, do.call, what = cbind)  # s is defined above
L[["4"]]  # returns a multivariate series with all the quarterlies