### Install ggnewscale Development Version

Source: https://github.com/eliocamp/ggnewscale/blob/master/README.md

Install the latest development version of ggnewscale directly from GitHub. Ensure the devtools package is installed first.

```r
# install.packages("devtools")
devtools::install_github("eliocamp/ggnewscale")
```

--------------------------------

### Working with guides() outside of scales

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

ggnewscale correctly tracks guide definitions even when attached with a standalone guides() call rather than inline in a scale. This example shows two independent guides() calls for the same aesthetic ('colour'), each retaining its own guide layout.

```r
library(ggplot2)
library(ggnewscale)

ggplot(head(iris, 10), aes(Sepal.Length, Sepal.Width)) +
  geom_point(aes(colour = factor(Petal.Length)), size = 4) +
  guides(colour = guide_legend(ncol = 2, nrow = 2, order = 1)) +

  new_scale_colour() +

  geom_point(aes(colour = factor(Petal.Width)), size = 2, shape = 17) +
  guides(colour = guide_legend(ncol = 1, nrow = 4, order = 2)) +

  labs(title = "Independent guides() calls per scale",
       colour = NULL)
```

--------------------------------

### Install ggnewscale Package

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

Install the ggnewscale package from CRAN for the stable version or from GitHub for the development version.

```r
install.packages("ggnewscale")
```

```r
# install.packages("devtools")
devtools::install_github("eliocamp/ggnewscale")
```

--------------------------------

### GPL Notice for Terminal Applications

Source: https://github.com/eliocamp/ggnewscale/blob/master/LICENSE.md

Display this short notice when a command-line program starts in interactive mode. It informs users about the warranty and redistribution terms, directing them to 'show w' and 'show c' for details.

```text
ggnewscale Copyright (C) 2018 Elio Campitelli
This program comes with ABSOLUTELY NO WARRANTY; for details type 'show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type 'show c' for details.
```

--------------------------------

### Install ggnewscale from CRAN

Source: https://github.com/eliocamp/ggnewscale/blob/master/README.md

Use this command to install the stable version of the ggnewscale package from the Comprehensive R Archive Network (CRAN).

```r
install.packages("ggnewscale")
```

--------------------------------

### Get Citation for ggnewscale Package

Source: https://github.com/eliocamp/ggnewscale/blob/master/README.md

Use this R code to retrieve the suggested citation for the ggnewscale package, including a BibTeX entry for LaTeX users.

```r
citation("ggnewscale")
#> To cite ggnewscale in publications use:
#> 
#>   Campitelli E (????). _ggnewscale: Multiple Fill and Colour Scales in
#>   'ggplot2'_. doi:10.5281/zenodo.2543762
#>   <https://doi.org/10.5281/zenodo.2543762>, R package version 0.5.2.
#> 
#> A BibTeX entry for LaTeX users is
#> 
#>   @Manual{R-ggnewscale,
#>     title = {ggnewscale: Multiple Fill and Colour Scales in 'ggplot2'},
#>     author = {Elio Campitelli},
#>     note = {R package version 0.5.2},
#>     doi = {10.5281/zenodo.2543762},
#>   }
```

--------------------------------

### Convenience Wrapper new_scale_colour() for Colour Scales

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

Use new_scale_colour() (or new_scale_color()) as a shorthand for new_scale('colour'). This example applies two independent color scales to mtcars data, one for cylinder count and another for gear count.

```r
library(ggplot2)
library(ggnewscale)

ggplot(mtcars, aes(mpg, disp)) +
  # First colour scale: cylinder count, qualitative brewer palette
  geom_point(aes(colour = factor(cyl)), size = 7) +
  scale_colour_brewer(type = "qual", name = "Cylinders",
                      guide = guide_legend(order = 1)) +

  new_scale_colour() +   # <-- open second colour scale

  # Second colour scale: gear count, Set1 palette
  geom_point(aes(colour = factor(gear)), size = 3) +
  scale_colour_brewer(palette = "Set1", name = "Gears",
                      guide = guide_legend(order = 2)) +

  labs(title = "mtcars: cylinders and gears as independent colour scales")
# Both legends appear; inner points show gears, outer points show cylinders
```

--------------------------------

### Open a New Scale Slot with new_scale()

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

Use new_scale() to insert a scale boundary, allowing subsequent geoms to use a new, independent scale for a specified aesthetic. Previously added layers remain unaffected. This example demonstrates two independent color scales for elevation contours and measurement points.

```r
library(ggplot2)
library(ggnewscale)

# Topographic surface data (built-in volcano dataset)
topography <- expand.grid(x = 1:nrow(volcano), y = 1:ncol(volcano))
topography$z <- c(volcano)

# Sparse point measurements at random locations
set.seed(42)
measurements <- data.frame(
  x     = runif(30, 1, 80),
  y     = runif(30, 1, 60),
  value = rnorm(30)
)

ggplot(mapping = aes(x, y)) +
  # Layer 1: contour lines coloured by elevation using the "D" (viridis) palette
  geom_contour(data = topography, aes(z = z, colour = after_stat(level))) +
  scale_colour_viridis_c(option = "D", name = "Elevation") +

  # --- Insert scale boundary: layers below get a NEW colour scale ---
  new_scale("colour") +

  # Layer 2: measurement points coloured by value using the "A" (magma) palette
  geom_point(data = measurements, aes(colour = value), size = 3) +
  scale_colour_viridis_c(option = "A", name = "Measurement") +

  labs(title = "Two independent colour scales on one plot")
# Result: two separate colour legends, one for elevation, one for measurements
```

--------------------------------

### Multiple new_scale_*() calls for independent scales

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

Call new_scale_*() repeatedly to create three or more independent scales for the same aesthetic. This example shows four independent fill scales on one plot, with each column of tiles having a distinct palette and four legends displayed.

```r
library(ggplot2)
library(ggnewscale)

data <- expand.grid(y = 1:4, x = 1:4)
data$z <- rep(c("a", "b"), length.out = nrow(data))

# Helper that creates one tile layer with its own fill scale
make_layer <- function(col_number, palette_number) {
  list(
    new_scale_fill(),
    geom_tile(
      data  = ~ .x[.x$x == col_number, ],
      aes(fill = z)
    ),
    scale_fill_brewer(
      name    = paste("Group", col_number),
      palette = palette_number,
      guide   = guide_legend(order = col_number)
    )
  )
}

ggplot(data, aes(x, y)) +
  make_layer(1, 2) +
  make_layer(2, 4) +
  make_layer(3, 6) +
  make_layer(4, 8) +
  labs(title = "Four independent fill scales on one plot")
```

--------------------------------

### Convenience Wrapper new_scale_fill() for Fill Scales

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

Use new_scale_fill() as a shorthand for new_scale('fill'). This is useful when combining geoms that require distinct fill palettes, such as geom_violin() and geom_point(). This example shows a discrete fill scale for gender and a continuous fill scale for score.

```r
library(ggplot2)
library(ggnewscale)

set.seed(5)
df <- data.frame(
  x      = floor(runif(100, 1, 5)),
  y      = floor(runif(100, 1, 10)),
  gender = sample(c("female", "male"), 100, replace = TRUE),
  score  = runif(100)
)

ggplot(df, aes(x, y, group = interaction(x, gender))) +
  # Fill scale 1: violin fill by gender (discrete)
  geom_violin(aes(fill = gender)) +
  scale_fill_discrete(name = "Gender", guide = guide_legend(order = 1)) +

  new_scale_fill() +   # <-- open second fill scale

  # Fill scale 2: point fill by continuous score
  geom_point(aes(fill = score), shape = 21, size = 3, inherit.aes = FALSE,
             data = df[sample(nrow(df), 30), ]) +
  scale_fill_viridis_c(name = "Score", guide = guide_colorbar(order = 2)) +

  labs(title = "Violin fill (discrete) + point fill (continuous)")
# Two separate fill legends are rendered correctly
```

--------------------------------

### Using rename_aes() to alias an aesthetic for a specific layer

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

Use rename_aes() to assign a custom alias to an aesthetic for the next layer. This is a lower-level alternative to new_scale(). The example renames 'colour' to 'topo_color' for the contour layer, then restores normal aesthetic names with clear_aes() before adding a point layer with its own 'colour' aesthetic.

```r
library(ggplot2)
library(ggnewscale)

topography <- expand.grid(x = 1:nrow(volcano), y = 1:ncol(volcano))
topography$z <- c(volcano)

set.seed(1)
measurements <- data.frame(
  x     = runif(30, 1, 80),
  y     = runif(30, 1, 60),
  value = rnorm(30)
)

ggplot(mapping = aes(x, y)) +
  # Rename "colour" -> "topo_color" for the next geom only
  rename_aes(topo_color = "colour") +
  geom_contour(
    data = topography,
    aes(z = z, topo_color = after_stat(level))
  ) +
  scale_colour_viridis_c(option = "D", name = "Elevation") +

  # Restore normal aesthetic names
  clear_aes() +

  geom_point(data = measurements, aes(colour = value), size = 3) +
  scale_colour_viridis_c(option = "A", name = "Measurement")
```

--------------------------------

### Using clear_aes() to remove rename_aes() mappings

Source: https://context7.com/eliocamp/ggnewscale/llms.txt

clear_aes() removes the active rename_aes() binding, restoring normal aesthetic name resolution for subsequent layers. This example shows the lifecycle of rename_aes() and clear_aes(), demonstrating how an alias is active for one geom and then removed for the next.

```r
library(ggplot2)
library(ggnewscale)

# rename_aes + clear_aes lifecycle:
p <- ggplot(mtcars, aes(mpg, disp)) +
  rename_aes(my_colour = "colour") +        # alias active
  geom_point(aes(my_colour = factor(cyl))) + # uses alias
  scale_colour_brewer(type = "qual") +
  clear_aes() +                              # alias removed
  geom_point(aes(colour = factor(gear)),     # back to standard name
             size = 1, shape = 1)

print(p)
```

--------------------------------

### Standard GPL Copyright Notice

Source: https://github.com/eliocamp/ggnewscale/blob/master/LICENSE.md

Include this notice at the beginning of each source file to state the exclusion of warranty and specify the terms of redistribution and modification under the GNU GPL.

```text
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) 2018 Elio Campitelli

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
```

--------------------------------

### Write Package Citation to Bib File

Source: https://github.com/eliocamp/ggnewscale/blob/master/README.md

Automate the process of writing package citation information to a .bib file using knitr, which can then be used for citations in R Markdown documents.

```r
knitr::write_bib(c("ggnewscale"), "packages.bib")
```

--------------------------------

### Add New Scale for Linetype Aesthetic

Source: https://github.com/eliocamp/ggnewscale/blob/master/README.md

Shows how to create a new scale for the 'linetype' aesthetic using `new_scale()`. This allows for multiple linetype scales within a single ggplot object.

```r
new_scale("linetype")
```

--------------------------------

### Add Multiple Color Scales to ggplot2 Plot

Source: https://github.com/eliocamp/ggnewscale/blob/master/README.md

Demonstrates how to use `new_scale_color()` to apply a second color scale to geoms added after its invocation. Requires `ggplot2` and `ggnewscale` libraries. The first scale is applied to `geom_contour` and the second to `geom_point`.

```r
library(ggplot2)
library(ggnewscale)
# Equivalent to melt(volcano)
topography <- expand.grid(x = 1:nrow(volcano), 
                          y = 1:ncol(volcano))
topography$z <- c(volcano)

# point measurements of something at a few locations
set.seed(42)
measurements <- data.frame(x = runif(30, 1, 80),
                           y = runif(30, 1, 60),
                           thing = rnorm(30))

ggplot(mapping = aes(x, y)) + 
  geom_contour(data = topography, aes(z = z, color = stat(level))) + 
  # Color scale for topography
  scale_color_viridis_c(option = "D") + 
  # geoms below will use another color scale
  new_scale_color() + 
  geom_point(data = measurements, size = 3, aes(color = thing)) + 
  # Color scale applied to geoms added after new_scale_color()
  scale_color_viridis_c(option = "A")
```

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