Sorting of Dataframe's Columns Within List Based on a Reference Vector

Question

I'm trying to sort a list filled with 5 different dataframes but with same column names, but just of different arrangements.

Reproducible Example:

d1 <- data.frame(y1 = c(1, 2, 3), y2 = c(4, 5, 6), y3 = c(5,6,7))
d2 <- data.frame(y2 = c(3, 2, 1), y3 = c(6, 5, 4), y1 = c(5,6,7))

my.list <- list(d1, d2)

> my.list
[[1]]
  y1 y2 y3
1  1  4  5
2  2  5  6
3  3  6  7

[[2]]
  y2 y3 y1
1  3  6  5
2  2  5  6
3  1  4  7

I'm trying to arrange each dataframe columns within the list into a specific order that I have already created under colnamesvec (see below.)

colnamesvec <- c("y3", "y2", "y1")

If I subset out each individual dataframe, I am able to achieve it using base R command. But is there a better way to loop through this easily to achieve what I want?

s <- my.list[[1]]
s[colnamesvec]

Thank you!

Ronak Shah · Accepted Answer · 2018-11-30 02:22:28Z

2

Use lapply and reorder the columns for each dataframe.

my.list[] <- lapply(my.list, function(x) x[colnamesvec])


my.list
#[[1]]
#  y3 y2 y1
#1  5  4  1
#2  6  5  2
#3  7  6  3

#[[2]]
#  y3 y2 y1
#1  6  3  5
#2  5  2  6
#3  4  1  7

This is assuming that all the columns in colnamesvec is present in each dataframe in the list.

answered Nov 30, 2018 at 2:22

Ronak Shah

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3 Comments

Maurits Evers Over a year ago

@RonakShah Sorry, noticed your post too late. There is some overlap with the linked post but it's not an exact duplicate; shall I re-open?

Ronak Shah Over a year ago

@MauritsEvers yes, imo it isn't an exact duplicate but I do have a feeling that there must be a post somewhere for this question, couldn't find though.

Maurits Evers Over a year ago

@RonakShah Ok, I've re-opened; if you find a more closely related post you can close it again. It does feel like one of those "asked-before" questions.

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