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rsortingrow

Sorting a column in descending order in R excluding the first row

I have a dataframe with 5 columns and a very large dataset. I want to sort by column 3. How do you sort everything after the first row? (When calling this function I want to end it with nrows)

Example output:

Original:

4
7
9
6
8

New:

4
9
8
7
6

Thanks!

Solution

  • If I'm correctly understanding what you want to do, this approach should work:

    z <- data.frame(x1 = seq(10), x2 = rep(c(2,3), 5), x3 = seq(14, 23))
zsub <- z[2:nrow(z),]
zsub <- zsub[order(-zsub[,3]),]
znew <- rbind(z[1,], zsub)

    Basically, snip off the rows you want to sort, sort them in descending order on column 3, then reattach the first row.

    And here's a piped version using dplyr, so you don't clutter the workspace with extra objects:

    library(dplyr)
z <- z %>%
    slice(2:nrow(z)) %>%
    arrange(-x3) %>%
    rbind(slice(z, 1), .)