# Make Your Plots Stand Out with Highlights

## Introduction

The `ggcharts` package currently offers two functions with a `highlight` parameter: `bar_chart()` and `lollipop_chart()`. The usage is the same for both functions.

    library(ggcharts)
    library(dplyr)
    data("biomedicalrevenue")
    revenue2018 <- biomedicalrevenue %>%
      filter(year == 2018)

## Basic Usage

In its most simple form the `highlight` feature can be used to highlight a single bar or lollipop.

    bar_chart(
      revenue2018,
      company,
      revenue,
      top_n = 10,
      highlight = "Roche"
    )

The color for the highlighted and non-highlighted values are automatically determined from the currently active `ggcharts` theme, i.e. `ggcharts_get_theme()`. Thus, changing the theme will change these colors.

    ggcharts_set_theme("theme_ng")
    bar_chart(
      revenue2018,
      company,
      revenue,
      top_n = 10,
      highlight = "Roche"
    )

## Changing the (Non-)Highlight Color

To set the highlight and non-highlight colors manually you will need to pass a `highlight_spec()` to the `highlight` argument.

    ggcharts_set_theme("theme_ggcharts")
    spec <- highlight_spec(
      what = "Roche",
      highlight_color = "black",
      other_color = "lightgray"
    )
    bar_chart(
      revenue2018,
      company,
      revenue,
      top_n = 10,
      highlight = spec
    )

## Highlighting Multiple Data Points

To highlight more than one value pass a vector to `highlight`.

    bar_chart(
      revenue2018,
      company,
      revenue,
      top_n = 10,
      highlight = c("Roche", "Novartis")
    )

To highlight multiple values in different colors you will need to use a `highlight_spec()` again.

    spec <- highlight_spec(
      what = c("Roche", "Novartis"),
      highlight_color = c("steelblue", "darkorange")
    )
    lollipop_chart(
      revenue2018,
      company,
      revenue,
      top_n = 10,
      highlight = spec
    )

## Highlight + Facet

The highlight feature is particularly useful when used in conjunction with the `facet` feature.

    biomedicalrevenue %>%
      filter(year %in% c(2012, 2014, 2016, 2018)) %>%
      bar_chart(
        company,
        revenue,
        facet = year,
        top_n = 12,
        highlight = "Bayer"
      )