观测值小于特定值R的下降因子 [英] Dropping factors which levels have observations smaller than a specific value-R

问题描述

让我有这样的数据帧(df1)，其因素有:

Let I have such data frame(df1) with factors:

factor1  factor2  factor3
-------  -------  -------
d        a         x
d        a         x
b        a         x
b        c         x
b        c         y
c        c         y
c        n         y
c        n         y
c        n         y

我想从这个数据框中删除其中一个元素少于3个观察值的因子.

I want to drop factors from this data frame which one of elements have less than 3 observations.

在此数据帧中，factor1具有3个级别(d，b和c).但是d级别具有频率2.因此我想从该数据帧中删除factor1.

In this data frame factor1 has 3 levels(d,b and c). However d level has frequency 2. So I want to drop factor1 from this data frame.

结果数据框应为:

factor2  factor3
-------  -------
a         x
a         x
a         x
c         x
c         y
c         y
n         y
n         y
n         y

如何使用R做到这一点?我会很高兴为您提供任何帮助.非常感谢.

How can I do this using R? I will be very glad for any help. Thanks a lot.

推荐答案

您可以尝试使用lapply和table:

df1[, lapply(c(1,2,3), FUN = function(x) min(table(df1[,x]))) >= 3]

，并且更通用一些:

df1[, lapply(1:ncol(df1), FUN = function(x) min(table(df1[,x]))) >= 3]

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