# Patterns ‘stripe’, ‘wave’, ‘crosshatch’, ‘weave’ - Parameters and Examples

    suppressPackageStartupMessages({
      library(ggplot2)
      library(ggpattern)
    })

## Introduction to the ‘stripe’, ‘wave’, ‘crosshatch’, and ‘weave’ patterns

- The ‘stripe’ pattern draws a set of (horizontal) straight lines.

- The ‘wave’ pattern draws a set of (horizontal) wavy lines.

- The ‘crosshatch’ pattern draws a set of vertical lines on top of a set of horizontal lines.

- The ‘weave’ pattern draws a set of vertical lines interlaced with a set of horizontal lines.

- For more info on these patterns see their `{gridpattern}` documentation:

  - `help("grid.pattern_stripe", package = "gridpattern")`
  - `help("grid.pattern_wave", package = "gridpattern")`
  - `help("grid.pattern_crosshatch", package = "gridpattern")`
  - `help("grid.pattern_weave", package = "gridpattern")`

## Pattern Parameters

aesthetic | description | default | possible values
--- | --- | --- | ---
pattern_colour | Stroke colour | ‘grey20’ | colour
pattern_fill | Fill colour | ‘grey80’ | colour
pattern_angle | Rotation angle | 30 | angle in degrees
pattern_density | Approx. fraction of area the pattern fills | 0.2 | value in range [0, 1] (fraction)
pattern_spacing | Spacing between repetitions of pattern | 0.05 | value in `pattern_units` grid units
pattern_xoffset | Shift pattern along x axis | 0 | value in `pattern_units` grid units
pattern_yoffset | Shift pattern along y axis | 0 | value in `pattern_units` grid units
pattern_units | Pattern grid unit | ‘snpc’ | `grid::unit()` unit i.e. ‘snpc’, ‘cm’, and ‘inches’
pattern_alpha | Alpha | NA | value in range [0, 1] or NA
pattern_linetype | Stroke linetype | 1 | linetype
pattern_size | Stroke linewidth | 1 | linewidth
pattern_type | Pattern type | NA | See wave and weave pattern documentation
pattern_subtype | Pattern subtype | NA | See weave pattern documentation
pattern_frequency | Frequency | 0.1 | Frequency of waves in ‘wave’ pattern

There are also a number of parameters for extra control of legend sizing and aspect ratio adjustments. See the ‘Pattern Parameters - Common’ for more information.

## Data

Standard data for all the example plots

    df <- data.frame(trt = c("a", "b", "c"), outcome = c(2.3, 1.9, 3.2))
    df
    #>   trt outcome
    #> 1   a     2.3
    #> 2   b     1.9
    #> 3   c     3.2

## Vanilla ggplot2

    ggplot(df, aes(trt, outcome)) +
      geom_col(aes(fill=trt),colour='black') +
      theme_bw() +
      labs(title = "Plain ggplot2")

## Use the `{ggpattern}` geom

- Use `ggpattern::geom_col_pattern()` instead of `ggplot2::geom_col()`.
- Set `pattern = 'stripe'`
- Default legends in `ggplot2` are usually too small to show off an example of the pattern, so it will usually be necessary to increase the key size.

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(aes(fill=trt),colour='black',
                       pattern='stripe') +
      theme_bw() +
      labs(title = "ggpattern") +
      theme(legend.key.size = unit(1.5, 'cm'))

## Mixing patterns

- Often we’ll want to mix patterns. To get the legend right we’ll often want to set them with a pattern scale function like ‘pattern_scale_manual()’ instead of simply setting them with the ‘pattern’ aesthetic.
- Here we’ll use the ‘stripe’ pattern and ‘wave’ pattern.
- The ‘wave’ pattern supports two subtypes: ‘triangle’ waves (default) have a zig-zag appearance whereas ‘sine’ waves have a curvy appearance.

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(aes(fill=trt, pattern=trt, pattern_type=trt),
                       colour='black', pattern_key_scale_factor=0.5,
                       pattern_spacing=0.7, pattern_frequency=0.7, pattern_units='cm') +
      theme_bw() +
      labs(title = "Use 'stripe' and 'wave' patterns") +
      theme(legend.key.size = unit(1.5, 'cm')) +
      scale_pattern_manual(values=c('stripe', 'wave', 'wave')) +
      scale_pattern_type_manual(values=c(NA, 'triangle', 'sine'))

## The Density Aesthetic

The aesthetic `pattern_density` roughly corresponds to the fraction of the filled area which should be covered by the pattern.

In the following plot the density of striping is increased to 50% of the fill area.

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(
        aes(fill=trt, pattern=trt),
        colour          = 'black',
        pattern_density = 0.5
      ) +
      theme_bw() +
      labs(title = "Fixed density of 0.5 (50% of the fill area)") +
      scale_pattern_manual(values=c('stripe', 'crosshatch', 'weave')) +
      theme(legend.key.size = unit(1.5, 'cm'))

## Weave types

The ‘weave’ pattern supports a rich set of weave types and subtypes including irregular ‘matt’, ‘twill’ (including ‘herringbone’ and ‘zigzag’ variations), and ‘satin’ weaves . See the weave pattern documentation for more information.

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(
        aes(pattern_fill2=trt, pattern_type=trt),
        pattern = 'weave',
        colour          = 'black',
        pattern_density = 1.0,
        pattern_fill = 'grey',
        pattern_key_scale_factor = 0.5,
      ) +
      theme_bw() +
      labs(title = "Some 'weave' types") +
      scale_pattern_type_manual(values=c('plain', 'twill', 'satin')) +
      theme(legend.key.size = unit(1.5, 'cm'))

## The Density Aesthetic as a Mapped Aesthetic

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(
        aes(fill = trt, pattern_density = trt),
        colour          = 'black',
        pattern         = 'stripe'
      ) +
      theme_bw() +
      labs(title = "Aesthetic Mapping of 'trt' to Density") +
      theme(legend.key.size = unit(1.5, 'cm'))

## The Density Aesthetic as a Mapped Aesthetic with Manual Scale

`scale_pattern_density_manual()` can be used to manually control how the variable is mapped to the density.

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(
        aes(fill = trt, pattern_density = trt),
        colour          = 'black',
        pattern         = 'stripe'
      ) +
      theme_bw() +
      labs(title = "Aesthetic Mapping of 'trt' to Density") +
      theme(legend.key.size = unit(1.5, 'cm')) +
      scale_pattern_density_manual(values = c(a = 0.1, b=0.3, c=0.5))

## The Spacing Aesthetic as a Mapped Aesthetic

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(
        aes(fill = trt, pattern_spacing = trt),
        colour          = 'black',
        pattern         = 'stripe'
      ) +
      theme_bw() +
      labs(title = "Aesthetic Mapping of 'trt' to Spacing") +
      theme(legend.key.size = unit(1.5, 'cm'))

## The Fill Aesthetic as a Mapped Aesthetic

    ggplot(df, aes(trt, outcome)) +
      geom_col_pattern(
        aes(fill = trt, pattern_fill = trt),
        colour          = 'black',
        pattern         = 'stripe'
      ) +
      theme_bw() +
      labs(title = "Aesthetic Mapping of 'trt' to Pattern Fill") +
      scale_pattern_fill_viridis_d() +
      theme(legend.key.size = unit(1.5, 'cm'))