Generate a density plot.

Easily generate a density plot of a numeric variable using ggplot2 with a simplified customization interface for common modifications with static (ggplot) and interactive (plotly) output options. The static output is useful for producing static reports (e.g. for manuscripts) and is readily customized further using ggplot2 syntax. The interactive output is helpful for exploring the data and producing dynamic html reports. See this blog post for an introduction to ggplot2.

plot_density(
  data,
  x,
  ...,
  fill_var = NULL,
  colour_var = NULL,
  xlab = NULL,
  ylab = NULL,
  title = NULL,
  title_hjust = 0.5,
  caption = NULL,
  caption_hjust = 0,
  fill_var_title = NULL,
  colour_var_title = NULL,
  xlim = c(NA, NA),
  xbreaks = ggplot2::waiver(),
  transform_x = FALSE,
  x_transformation = "log10",
  x_var_labs = ggplot2::waiver(),
  fill_var_order = NULL,
  colour_var_order = NULL,
  fill_var_labs = NULL,
  colour_var_labs = NULL,
  fill_var_values = NULL,
  colour_var_values = NULL,
  palette = c("plasma", "C", "magma", "A", "inferno", "B", "viridis", "D", "cividis",
    "E"),
  palette_direction = c("d2l", "l2d"),
  palette_begin = 0,
  palette_end = 1,
  alpha = 0.6,
  greyscale = FALSE,
  line_size = 1.1,
  rug = FALSE,
  rug_colour = "black",
  rug_alpha = 0.8,
  dnorm = FALSE,
  dnorm_colour = "black",
  dnorm_line_type = c("dashed", "solid", "dotted", "dotdash", "longdash", "twodash"),
  dnorm_line_size = 1.1,
  dnorm_alpha = 0.6,
  theme = c("bw", "classic", "grey", "light", "dark", "minimal"),
  text_size = 14,
  font = c("sans", "serif", "mono"),
  facet_var = NULL,
  facet_var_order = NULL,
  facet_var_labs = NULL,
  facet_var_strip_position = c("top", "bottom"),
  facet_var_text_bold = TRUE,
  legend_position = c("right", "left", "top", "bottom"),
  omit_legend = FALSE,
  interactive = FALSE,
  aesthetic_options = FALSE
)

Arguments

data

A data frame or tibble containing the dependent measure "x" and any grouping variables.

x

The name of a numeric variable you want a density plot of (quoted or unquoted), e.g. x = "variable" or x = variable.

...

graphical parameters (not associated with variables) to be passed to geom_density, e.g. colour or fill, to be applied to all curves. See the ggplot2 aesthetic specifications vignette for options.

fill_var

Use if you want to assign a variable to the density curve fill colour, e.g. fill_var = "grouping_variable" or fill_var = grouping_variable. Produces separate curves for each level of the fill variable. See aes for details.

colour_var

Use if you want to assign a variable to the density curve outline colour, e.g. colour_var = "grouping_variable" or colour_var = grouping_variable. Produces separate curves for each level of the colour variable. See aes for details.

xlab

Specify/overwrite the x-axis label using a character string, e.g. "x-axis label"

ylab

Specify/overwrite the y-axis label using a character string, e.g. "y-axis label"

title

Add a main title to the plot using a character string, e.g. "Density graph of X"

title_hjust

Left-to-right/horizontal justification (alignment) of the main plot title. Accepts values from 0 (far left) to 1 (far right). Default is 0.5 (centre).

caption

Add a figure caption to the bottom of the plot using a character string.

caption_hjust

Left-to-right/horizontal justification (alignment) of the caption. Accepts values from 0 (far left) to 1 (far right). Default is 0 (left).

fill_var_title

If a variable has been assigned to fill using fill_var, this allows you to modify the variable label in the plot legend.

colour_var_title

If a variable has been assigned to colour using colour_var, this allows you to modify the variable label in the plot legend.

xlim

Specify the x-axis limits, e.g. xlim = c(lower_limit, upper_limit). Use NA for the existing minimum or maximum value of x, e.g. the default is xlim = c(NA, NA).

xbreaks

This allows you to change the break points to use for tick marks via a numeric vector. seq is particularly useful here. See scale_x_continuous for details. If xbreaks is specified, then xlim should be also.

transform_x

Would you like to transform the x axis? (TRUE or FALSE)

x_transformation

If transform_x = TRUE, this determines the transformation to be applied. Common choices include "log10" (the default), "log2", "sqrt", or "exp". See scale_continuous for details.

x_var_labs

Allows you to modify the labels displayed with the x-axis tick marks. See scale_x_continuous for details.

fill_var_order

If a variable has been assigned to fill using fill_var, this allows you to modify the order of the variable groups, e.g. fill_var = grouping_variable, fill_var_order = c("group_2", "group_1"). See fct_relevel for details.

colour_var_order

If a variable has been assigned to colour using colour_var, this allows you to modify the order of the variable groups, e.g. colour_var = grouping_variable, fill_var_order = c("group_2", "group_1"). See fct_relevel for details.

fill_var_labs

If a variable has been assigned to fill using fill_var, this allows you to modify the labels of the variable groups, e.g. fill_var = grouping_variable, fill_var_labs = c("group_1_new_label" = "group_1_old_label", "group_2_new_label" = "group_2_old_label"). See fct_recode for details.

colour_var_labs

If a variable has been assigned to colour using colour_var, this allows you to modify the labels of the variable groups, e.g. colour_var = grouping_variable, colour_var_labs = c("group_1_new_label" = "group_1_old_label", "group_2_new_label" = "group_2_old_label"). See fct_recode for details.

fill_var_values

If a variable has been assigned to fill using fill_var, this allows you to modify the colours assigned to the fill of each of the variable groups, e.g. fill_var = grouping_variable, fill_var_values = c("blue", "red"). See scale_fill_manual for details. For the colour options available in base R, see colour_options.

colour_var_values

If a variable has been assigned to colour using colour_var, this allows you to modify the colours assigned to the outline of each of the variable groups, e.g. colour_var = grouping_variable, colour_var_values = c("blue", "red"). See scale_fill_manual for details. For the colour options available in base R, see colour_options.

palette

If a variable is assigned to fill_var or colour_var, this determines which viridis colour palette to use. Options include "plasma" or "C" (default), "magma" or "A", "inferno" or "B", "viridis" or "D", and "cividis" or "E". See this link for examples. You can override these colour palettes with fill_var_values or colour_var_values.

palette_direction

Choose "d2l" for dark to light (default) or "l2d" for light to dark.

palette_begin

Value between 0 and 1 that determines where along the full range of the chosen colour palette's spectrum to begin sampling colours. See scale_fill_viridis_d for details.

palette_end

Value between 0 and 1 that determines where along the full range of the chosen colour palette's spectrum to end sampling colours. See scale_fill_viridis_d for details.

alpha

This adjusts the transparency/opacity of the density plot(s), with acceptable values ranging from 0 = 100% transparent to 1 = 100% opaque.

greyscale

Set to TRUE if you want the plot converted to greyscale.

line_size

This modifies the thickness of the density curve.

rug

Set this to TRUE to add rug lines to the bottom of the plot.

rug_colour

Determines the colour of the rug lines (if rug = TRUE).

rug_alpha

This adjusts the transparency/opacity of the rug lines (if rug = TRUE) with valid values ranging from 0 = 100% transparent to 1 = 100% opaque.

dnorm

Set this to TRUE to add a normal/Gaussian density curve to the plot. Ignored if x is a date vector or "transform_x" = TRUE.

dnorm_colour

Determines the colour of the normal density curve (if dnorm = TRUE).

dnorm_line_type

The type of line to use to draw the normal density curve (if dnorm = TRUE). Options include "dashed" (default), "solid", "dotted", "dotdash", "longdash", and "twodash".

dnorm_line_size

Adjusts the thickness of the normal density curve (if dnorm = TRUE).

dnorm_alpha

This adjusts the transparency/opacity of the normal density curve (if dnorm = TRUE) with valid values ranging from 0 = 100% transparent to 1 = 100% opaque.

theme

Adjusts the theme using 1 of 6 predefined "complete" theme templates provided by ggplot2. Currently supported options are: "classic", "bw" (the elucidate default), "grey" (the ggplot2 default), "light", "dark", & "minimal". See theme_bw for more information.

text_size

This controls the size of all plot text. Default = 14.

font

This controls the font of all plot text. Default = "sans" (Arial). Other options include "serif" (Times New Roman) and "mono" (Courier New).

facet_var

Use if you want separate plots for each level of a grouping variable (i.e. a faceted plot), e.g. facet_var = "grouping_variable" or facet_var = grouping_variable. See facet_wrap for details.

facet_var_order

If a variable has been assigned for faceting using facet_var, this allows you to modify the order of the variable groups, e.g. facet_var = grouping_variable, facet_var_order = c("group_2", "group_1"). See fct_relevel for details.

facet_var_labs

If a variable has been assigned for faceting using facet_var, this allows you to modify the labels of the variable groups which will appear in the facet strips, e.g. facet_var = grouping_variable, facet_var_labs = c("group_1_new_label" = "group_1_old_label", "group_2_new_label" = "group_2_old_label"). See fct_recode for details.

facet_var_strip_position

If a variable has been assigned for faceting using facet_var, this allows you to modify the position of the facet strip labels. Sensible options include "top" (the default) or "bottom".

facet_var_text_bold

If a variable has been assigned for faceting using facet_var, this allows you to use boldface (TRUE/default or FALSE) for the facet strip label text.

legend_position

This allows you to modify the legend position. Options include "right" (the default), "left", "top", & "bottom".

omit_legend

Set to TRUE if you want to remove/omit the legends.

interactive

Determines whether a static ggplot object or an interactive html plotly object is returned. See ggplotly for details.

aesthetic_options

If set to TRUE, opens a web browser to the tidyverse online aesthetic options vignette.

Value

A ggplot object or plotly object depending on whether static or interactive output was requested.

References

Wickham, H. (2016). ggplot2: elegant graphics for data analysis. New York, N.Y.: Springer-Verlag.

See also

geom_density, dnorm, geom_line, geom_rug, ggplotly

Author

Craig P. Hutton, Craig.Hutton@gov.bc.ca

Examples

data(mtcars) #load the mtcars data

plot_density(mtcars, x = mpg)


# \donttest{
plot_density(mtcars, x = mpg, transform_x = TRUE, x_transformation = "log2")


plot_density(mtcars, x = mpg, transform_x = TRUE,
             x_transformation = "log10") #default transformation


plot_density(mtcars, x = mpg, transform_x = TRUE,
             x_transformation = "sqrt") #default transformation


plot_density(mtcars, x = mpg, fill_var = cyl, fill_var_labs = c("four" = "4"))


plot_density(mtcars, x = mpg, fill_var = cyl, fill_var_title = "# cyl",
             interactive = TRUE)


plot_density(mtcars,
             x = mpg,
             fill_var = am,
             fill_var_order = c("1", "0"),
             fill_var_labs = c("manual" = "0",
                               "automatic" = "1"),
             fill_var_values = c("blue4", "red4"),
             fill_var_title = "transmission")


plot_density(mtcars,
             x = mpg,
             colour_var = cyl,
             colour_var_order = c("6", "8", "4"),
             colour_var_labs = c("six" = "6", "eight" = "8"),
             colour_var_values = c("blue3", "red3", "green3"),
             colour_var_title = "# cylinders")


#interactive version

plot_density(mtcars, mpg, fill_var = cyl, interactive = TRUE)

# }