在应用中使用ifelse [英] Using ifelse Within apply

问题描述

我正在尝试使数据集中的新列为每一行提供单个输出，具体取决于现有列的输入.

I am trying to make a new column in my dataset give a single output for each and every row, depending on the inputs from pre-existing columns.

在此输出列中，如果给定行中的任何输入值都为"0"，我希望为"". 否则(如果所有输入都不为0)，我希望该行的输出为输入的唯一值的数量.

In this output column, I desire "NA" if any of the input vales in a given row are "0". Otherwise (if none of the inputs are 0), I want the output for that row to be the number of unique values of the inputs.

我认为该解决方案将使用嵌套在 apply 函数中的 ifelse 函数，但是出现一个我不理解的错误.

I thought that the solution would use an ifelse function nested within an apply function, but I get an error that I do not understand.

data$output <- apply(data, 1, function(x) {ifelse(x == 0, NA, length(unique(x)))})

$<-.data.frame(*tmp*，输出"，值= c(3L，3L，3L，3L，: 替换有3行，数据有4

Error in $<-.data.frame(*tmp*, "output", value = c(3L, 3L, 3L, 3L, : replacement has 3 rows, data has 4

我不知道替换为什么有3行，因为我认为对4行中的每行都执行相同的功能.

I do not know why the replacement has 3 rows, as I thought apply just does the same function to each of my 4 rows.

推荐答案

您要检查行中是否有任何变量为0，因此需要在ifelse中使用any(x==0)而不是x == 0声明:

You want to check if any of the variables in a row are 0, so you need to use any(x==0) instead of x == 0 in the ifelse statement:

apply(data, 1, function(x) {ifelse(any(x == 0), NA, length(unique(x)))})
# [1]  1 NA  2

基本上，如果ifelse的第一个参数的长度为n，则返回长度为n的向量.您希望每行一个值，但是要用x==0传递多个值(您传递的值的数量等于数据框中的列数).

Basically ifelse returns a vector of length n if its first argument is of length n. You want one value per row, but are passing more than one with x==0 (the number of values you're passing is equal to the number of columns in your data frame).

数据:

(data <- data.frame(a=c(1, 2, 3), b=c(1, 0, 1)))
#   a b
# 1 1 1
# 2 2 0
# 3 3 1

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