使用 ifelse 添加具有条件值的新列 [英] Adding new column with conditional values using ifelse

问题描述

我有一个包含超过 400.000 个观察值的数据框，我正在尝试向其中添加一列，其值取决于另一列，有时取决于多个列.

I have a data frame with more than 400.000 observations and I'm trying to add a column to it which its values depend on another column and sometimes multiple ones.

这是我正在尝试做的一个更简单的例子:

Here is a simpler example of what I'm trying to do :

# Creating a data frame 

M <- data.frame(c("A","B","C"),c(5,100,60))

names(M) <- c("Letter","Number")

#adding a column 

M$Size <- NA

# if Number <= 50 Size is small, 
# if Number is between 50 and 70, Size is Medium
# if Number is Bigger than 70, Size is Big

ifelse (M$Number <=50, M$Size <-"Small",
        ifelse(M$Number <= 70,
        M$Size <- "Medium",
        M$Size <- "Big"
        ))

当我运行代码时，我得到的输出是:

When I run the Code, the output I get is :

[1] "Small"  "Big"    "Medium"

但 M 中的大小"列始终是 ifelse 函数中的最后一个条件:

But the "Size" column in M is always the last condition in the ifelse function :

> print (M)
  Letter Number Size
1      A      5  Big
2      B    100  Big
3      C     60  Big

我想要的结果:

> print (M)
  Letter Number Size
1      A      5  Small
2      B    100  Big
3      C     60  Medium

我可以通过设置每个条件的子集来解决问题subset 并使用 rbind 得到我想要的结果，但代码会很长，因为原始数据框我工作量很大，运行需要更多时间.所以我想知道如何解决这个问题?

I can solve the problem by subsetting each conditionsubset and using rbind to get the result I want but the code will be very long and since the original data frame I'm working on is big, it'll take more time to run. So I'm wondering how can I fix this issue ?

推荐答案

这会帮助你 -

# Creating a data frame 

M <- data.frame(c("A","B","C"),c(5,100,60))

names(M) <- c("Letter","Number")

#adding a column 


# if Number <= 50 Size is small, 
# if Number is between 50 and 70, Size is Medium
# if Number is Bigger than 70, Size is Big

# M$Size[M$Number <= 50] <- "Small"
# Edit: No need to subset "Small"
M$Size <- "Small"
M$Size[M$Number >50 & M$Number<70] <- "Medium"
M$Size[M$Number > 70] <- "Big"

#      Letter Number   Size
# 1      A      5      Small
# 2      B    100      Big
# 3      C     60      Medium

在 R-Fiddle

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