在 R 中，如何选择在某个行索引中包含某个值的某些列？

Question

Let's suppose we have a dataframe like such:

X <- data.frame(A = c(1,3,1), B = c(2,3,9), C = c(3,4,8))

[A, B, C]
[1, 3, 1]
[2, 3, 9]
[3, 4, 8]

I only want to select columns where its value in row 3 is greater than 5. In this case, only B and C would be selected. Furthermore, I only want to reference that row by its index. Like row 528, or 326.

What is the syntax for doing this? I checked online and it appeared dplyr's select would work... but I haven't figured out a good way to put it to use.

Answer 1

You could use :

row <- 3
X[row, X[row, ] > 5]

#  B C
#3 9 8

This select row number row and columns where value in row is greater than 5.

Using dplyr :

library(dplyr)
X %>% slice(row) %>% select_if(. > 5)