Question

我有一个包含超过400,000个观测数据的数据框，我正在尝试为其添加一个列，其值取决于另一列，有时还有多个列。

这是我正在尝试做的一个更简单的例子：

# 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：

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

但是M中的“Size”列始终是ifelse函数中的最后一个条件：

> 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

我可以通过对每个条件subset进行子集化并使用rbind来获得我想要的结果来解决问题，但代码将会非常长，因为我正在处理的原始数据框很大，这需要更多的时间来运行。所以我想知道如何解决这个问题？

Answer 1

使用cut：

M$Size <- cut(M$Number, breaks = c(-Inf, 50, 70, Inf), 
                        labels = c("small", "medium", "large"))
#   etter Number   Size
#1      A      5  small
#2      B    100  large
#3      C     60 medium

Answer 2

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

上查看

Answer 3

同样的想法，但改为分配它。不需要包裹。

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

结果：

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

使用ifelse添加带有条件值的新列

3 个答案: