facet_wrap {ggplot2} | R Documentation

## Wrap a 1d ribbon of panels into 2d.

### Description

Most displays are roughly rectangular, so if you have a categorical variable with many levels, it doesn't make sense to try and display them all in one row (or one column). To solve this dilemma, `facet_wrap` wraps a 1d sequence of panels into 2d, making best use of screen real estate.

### Usage

    facet_wrap(facets, nrow = NULL, ncol = NULL, scales = "fixed",
      shrink = TRUE, labeller = "label_value", as.table = TRUE,
      switch = NULL, drop = TRUE, dir = "h")

### Arguments

`facets` | Either a formula or character vector. Use either a one sided formula, `~a + b`, or a character vector, `c("a", "b")`.
`nrow, ncol` | Number of rows and columns.
`scales` | should Scales be fixed (`"fixed"`, the default), free (`"free"`), or free in one dimension (`"free_x"`, `"free_y"`).
`shrink` | If `TRUE`, will shrink scales to fit output of statistics, not raw data. If `FALSE`, will be range of raw data before statistical summary.

`labeller`

A function that takes one data frame of labels and returns a list or data frame of character vectors. Each input column corresponds to one factor. Thus there will be more than one with formulae of the type `~cyl + am`. Each output column gets displayed as one separate line in the strip label. This function should inherit from the "labeller" S3 class for compatibility with `labeller()`. See `label_value` for more details and pointers to other options.

`as.table` | If `TRUE`, the default, the facets are laid out like a table with highest values at the bottom-right. If `FALSE`, the facets are laid out like a plot with the highest value at the top-right.
`switch` | By default, the labels are displayed on the top of the plot. If `switch` is `"x"`, they will be displayed to the bottom. If `"y"`, they will be displayed to the left, near the y axis.
`drop` | If `TRUE`, the default, all factor levels not used in the data will automatically be dropped. If `FALSE`, all factor levels will be shown, regardless of whether or not they appear in the data.
`dir` | Direction: either "h" for horizontal, the default, or "v", for vertical.

### Examples

    ggplot(mpg, aes(displ, hwy)) +
      geom_point() +
      facet_wrap(~class)

    # Control the number of rows and columns with nrow and ncol
    ggplot(mpg, aes(displ, hwy)) +
      geom_point() +
      facet_wrap(~class, nrow = 4)

    # You can facet by multiple variables
    ggplot(mpg, aes(displ, hwy)) +
      geom_point() +
      facet_wrap(~ cyl + drv)
    # Or use a character vector:
    ggplot(mpg, aes(displ, hwy)) +
      geom_point() +
      facet_wrap(c("cyl", "drv"))

    # Use the `labeller` option to control how labels are printed:
    ggplot(mpg, aes(displ, hwy)) +
      geom_point() +
      facet_wrap(c("cyl", "drv"), labeller = "label_both")

    # To change the order in which the panels appear, change the levels
    # of the underlying factor.
    mpg$class2 <- reorder(mpg$class, mpg$displ)
    ggplot(mpg, aes(displ, hwy)) +
      geom_point() +
      facet_wrap(~class2)

    # By default, the same scales are used for all panels. You can allow
    # scales to vary across the panels with the `scales` argument.
    # Free scales make it easier to see patterns within each panel, but
    # harder to compare across panels.
    ggplot(mpg, aes(displ, hwy)) +
      geom_point() +
      facet_wrap(~class, scales = "free")

    # To repeat the same data in every panel, simply construct a data frame
    # that does not contain the facetting variable.
    ggplot(mpg, aes(displ, hwy)) +
      geom_point(data = transform(mpg, class = NULL), colour = "grey85") +
      geom_point() +
      facet_wrap(~class)

    # Use `switch` to display the facet labels near an axis, acting as
    # a subtitle for this axis. This is typically used with free scales
    # and a theme without boxes around strip labels.
    ggplot(economics_long, aes(date, value)) +
      geom_line() +
      facet_wrap(~variable, scales = "free_y", nrow = 2, switch = "x") +
      theme(strip.background = element_blank())

[Package ggplot2 version 2.1.0 Index]