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Annemarie
Annemarie

Reputation: 609

order data.frame on non-numerical value

I have a data.frame that looks like this:

320    Dutch  A7     3

321    Dutch  A8     3

322    Dutch  A9     4

323    Dutch A10     1

324    Dutch A11     4

327    Dutch A14     4

325    Dutch A12     3

328    Dutch A15    10

326    Dutch A13     1

329    Dutch A16     3

How can I order it so all the A1, A2, etc. are in order alphabetically and numerically, so that I get:

320    Dutch  A7     3

321    Dutch  A8     3

322    Dutch  A9     4

323    Dutch A10     1

324    Dutch A11     4

325    Dutch A12     3

326    Dutch A13     1

327    Dutch A14     4

328    Dutch A15    10

329    Dutch A16     3

Thank you!

Upvotes: 0

Views: 1604

Answers (2)

Richie Cotton
Richie Cotton

Reputation: 121077

Forget the data frame part for now. Here's a sample vector that you want to order

x <- paste(
  rep.int(LETTERS[1:3], 16),
  rep.int(1:16, 3),
  sep = ""
)
y <- sample(x)

Just calling sort(y) won't work because number get sorted into lexographical order, so you get something like A1, A10, A11, ...

Instead, use substring to split the column into a letter and a number.

indexer <- data.frame(
  letter = substring(y, 1, 1),
  number = as.numeric(substring(y, 2))
)

Then, as aL3xa suggested, call order to order the resulting data frame.

o <- with(indexer, order(letter, number))
y[o]

To get this to work with a data frame, simply replace y with your_data$index_column.

Upvotes: 1

aL3xa
aL3xa

Reputation: 36080

You kind-of answered your own question. See help for order function. And also see this rant.

Upvotes: 1

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