可视化 | ggplot2 2.2.0 新版本11月发布

最新版本安装

# install.packages("devtools")

devtools::install_github("hadley/ggplot2")

如果发现错误，请告知，并暂时使用旧版

install.packages("ggplot2")

ggplot2 2.2.0 主要更新内容包括以下几点:

（1）Subtitles and captions

（2）A large rewrite of the facetting system

（3）Improved theme options

（4）Better stacking

（5）Numerous bug fixes and minor improvements

Subtitles and captions

ggplot(mpg, aes(displ, hwy)) +

  geom_point(aes(color = class)) +

  geom_smooth(se = FALSE, method = "loess") +

  labs(

    title = "Fuel efficiency generally decreases with engine size",

    subtitle = "Two seaters (sports cars) are an exception because of their light weight",

    caption = "Data from fueleconomy.gov"

  )

These are controlled by the theme settings plot.subtitle and plot.caption.

The plot title is now aligned to the left by default. To return to the previous centering, use theme(plot.title = element_text(hjust = 0.5)).

Facets

The facet and layout implementation has been moved to ggproto and received a large rewrite and refactoring. This will allow others to create their own facetting systems, as descrbied in the Extending ggplot2 vignette. Along with the rewrite a number of features and improvements has been added, most notably:

• Functions in facetting formulas, thanks to Dan Ruderman.

  ggplot(diamonds, aes(carat, price)) + 
  
    geom_hex(bins = 20) + 
  
    facet_wrap(~cut_number(depth, 6))

• Axes were dropped when the panels in facet_wrap() did not completely fill the rectangle. Now, an axis is drawn underneath the hanging panels:
  

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

  
  

• It is now possible to set the position of the axes through the position argument in the scale constructor:

  ggplot(mpg, aes(displ, hwy)) + 
  
    geom_point() + 
  
    scale_x_continuous(position = "top") + 
  
    scale_y_continuous(position = "right")

  
  

• You can display a secondary axis that is a one-to-one transformation of the primary axis with the sec.axis argument:

  ggplot(mpg, aes(displ, hwy)) + 
  
    geom_point() + 
  
    scale_y_continuous(
  
      "mpg (US)", 
  
      sec.axis = sec_axis(~ . * 1.20, name = "mpg (UK)")
  
    )

  
  

• Strips can be placed on any side, and the placement with respect to axes can be controlled with the strip.placement theme option.

  ggplot(mpg, aes(displ, hwy)) + 
  
    geom_point() + 
  
    facet_wrap(~ drv, strip.position = "bottom") + 
  
    theme(
  
      strip.placement = "outside",
  
      strip.background = element_blank(),
  
      strip.text = element_text(face = "bold")
  
    ) +
  
    xlab(NULL)

  
  

Theming

• Blank elements can now be overridden again so you get the expected behavior when setting e.g. axis.line.x.

• element_line() gets an arrow argument that lets you put arrows on axes.

  arrow <- arrow(length = unit(0.4, "cm"), type = "closed")
  
  
  
  ggplot(mpg, aes(displ, hwy)) + 
  
    geom_point() + 
  
    theme_minimal() + 
  
    theme(
  
      axis.line = element_line(arrow = arrow)
  
    )

• Control of legend styling has been improved. The whole legend area can be aligned according to the plot area and a box can be drawn around all legends:

  ggplot(mpg, aes(displ, hwy, shape = drv, colour = fl)) + 
  
    geom_point() + 
  
    theme(
  
      legend.justification = "top", 
  
      legend.box.margin = margin(3, 3, 3, 3, "mm"), 
  
      legend.box.background = element_rect(colour = "grey50")
  
    )

  
  

• panel.margin and legend.margin have been renamed to panel.spacing and legend.spacing respectively as this better indicates their roles. A new legend.margin has been actually controls the margin around each legend.

• When computing the height of titles ggplot2, now inclues the height of the descenders (i.e. the bits g and y that hang underneath). This makes improves the margins around titles, particularly the y axis label. I have also very slightly increased the inner margins of axis titles, and removed the outer margins.

• The default themes has been tweaked by Jean-Olivier Irisson making them better match theme_grey().

• Lastly, the theme() function now has named arguments so autocomplete and documentation suggestions are vastly improved.

Stacking bars

position_stack() and position_fill() now stack values in the reverse order of the grouping, which makes the default stack order match the legend.

avg_price <- diamonds %>% 

  group_by(cut, color) %>% 

  summarise(price = mean(price)) %>% 

  ungroup() %>% 

  mutate(price_rel = price - mean(price))



ggplot(avg_price) + 

  geom_col(aes(x = cut, y = price, fill = color))

(Note also the new geom_col() which is short-hand for geom_bar(stat = "identity"), contributed by Bob Rudis.)

Additionally, you can now stack negative values:

ggplot(avg_price) + 

  geom_col(aes(x = cut, y = price_rel, fill = color))

The overall ordering cannot necessarily be matched in the presence of negative values, but the ordering on either side of the x-axis will match.

If you want to stack in the opposite order, try forcats::fct_rev():

ggplot(avg_price) + 

  geom_col(aes(x = cut, y = price, fill = fct_rev(color)))