G. Gip - 2 months ago 6x
R Question

# R: Re-order numeric vector by name using custom order

I have a a numeric vector and want to re-order by name, using a custom order.

``````x <- sample(1:20, 5)
names(x) <- c("feb", "may", "mar", "jan", "apr")
x
feb may mar jan apr
7  10   5  13  11
``````

As you can see, the vectors are not in month order

## Desired output

I wish to re-order this character vector through month order using the names, i.e.
`jan, feb, mar, apr, may...`

How is this possible?

note: I am after a method that can be used on all names/character strings, rather than specifically date objects

We can convert the `names` of 'x' to `factor` and settting the `levels` to the `month.abb` in lowercase, apply the `order` and get the 'x' in that order.

``````x[order(factor(names(x), levels=tolower(month.abb)))]
jan feb mar apr may
13  7   5  11  10
``````

The conversion to `factor` with `levels` specified can be applied to any character vector in a custom order, otherwise, by default, the ordering is based on alphabetical order i.e.

``````x[order(names(x))]
``````

Suppose, if want the order to be say, 'jan', 'mar', 'apr', 'may', 'feb', use that as `levels` in the `factor` call

``````x[order(factor(names(x), levels = c('jan', 'mar', 'apr', 'may', 'feb')))]
``````

As the OP posted another vector in a custom order in the comments

``````x1 <- c(icecream = 3, jelly = 4, fruit = 5)
x1[order(factor(names(x1), levels = c("jelly", "fruit", "icecream")))]
#   jelly    fruit icecream
#      4        5        3
``````