返回数据框中列中特定值的行号 [英] Return row number(s) for a particular value in a column in a dataframe

问题描述

我有一个数据框 (df)，我想知道如何在 中返回特定值 (2585) 的行号同一数据框的第 4 列 (height_chad1)?

I have a data frame (df) and I was wondering how to return the row number(s) for a particular value (2585) in the 4th column (height_chad1) of the same data frame?

我试过了:

row(mydata_2$height_chad1, 2585)

并且我收到以下错误:

Error in factor(.Internal(row(dim(x))), labels = labs) : 
  a matrix-like object is required as argument to 'row'

是否有等效的代码行适用于数据帧而不是类似矩阵的对象?

Is there an equivalent line of code that works for data frames instead of matrix-like objects?

任何帮助将不胜感激.

推荐答案

使用 which(mydata_2$height_chad1 == 2585)

简短的例子

df <- data.frame(x = c(1,1,2,3,4,5,6,3),
                 y = c(5,4,6,7,8,3,2,4))
df
  x y
1 1 5
2 1 4
3 2 6
4 3 7
5 4 8
6 5 3
7 6 2
8 3 4

which(df$x == 3)
[1] 4 8

length(which(df$x == 3))
[1] 2

count(df, vars = "x")
  x freq
1 1    2
2 2    1
3 3    2
4 4    1
5 5    1
6 6    1

df[which(df$x == 3),]
  x y
4 3 7
8 3 4

正如 Matt Weller 指出的，您可以使用 length 函数.plyr 中的 count 函数可用于返回每个唯一列值的计数.

As Matt Weller pointed out, you can use the length function. The count function in plyr can be used to return the count of each unique column value.

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