第 6 章 Guide, Facet and Theme

6.1 Guides (axes+legend)

• reference: https://ggplot2.tidyverse.org/reference/guides.html

• Guides: 圖形aes mapping說明。主要由座標軸（axes）及圖例（legend）使讀者易於理解aes mapping關係，其設計更動主要透過下面兩個layers:

x/y的說明透過：

• axes: +scale_<x or y>_...()

其他aes mapping說明透過：

• legend: +guide(<aes name>=...)

6.1.1 Guides: axes

• +scale_<x or y>_...()

6.1.1.1 second axis: sec_axis()

• 兩個「不同範圍」的y值，有「相同的x」，其中：
  (yL,x) 要使用左邊內訂y座標軸；(yR,x)要使用右邊第二座標軸(second axis).

  • 步驟1：定義函數轉換(\(f\)及\(f^{-1}\))
    先將\(yR\)經過一個函數f轉換成在Y-left axis limits範圍的\(yL^*\)，即: \[yL^*=f(yR)\] 形成新的\((yL^*,x)\)資料。 \[ yR\stackrel{f}{\rightarrow}yL^{*}\\ yR\stackrel{f^{-1}}{\leftarrow}yL^{*} \]

  • 步驟2：yR資料轉換
    將\((yL,x)\)與轉換後的\((yL^*,x)\)畫在一起。

  • 步驟3：設定右Y軸
    加上右Y軸並告訴ggplot，「左Y」如何對應到「右Y」——使用scale_y_...() layer, 更改設定sec.axis=sec_axis(...), 其中：

sec_axis(trans = f_inverse, name = waiver(), breaks = waiver(),
  labels = waiver())

• f_inverse: \(f^{-1}\) 函數名稱

範例

billionaire <- 
  read_csv("https://www.dropbox.com/s/cpu4f09x3j78wqi/billionaire.csv?dl=1") %>%
  rename(
    "Year"="X1"
  )

billionaire %>%
  ggplot()+geom_line(
    aes(x=Year,y=Russia)
  ) +
  scale_y_continuous(
    breaks=seq(0,200,by=50)
  ) +
  theme_linedraw()-> plot_russia

billionaire %>%
  ggplot()+geom_line(
    aes(x=Year,y=World)
  )+
  scale_y_continuous(
    breaks=seq(0,2000,by=500)
  ) +
  theme_linedraw()-> plot_world

步驟一：定義\(f\)及\(f^{-1}\)

f <- function(x) x/10
f_inverse <- function(f_value) 10*f_value

步驟二：轉換\(yR\)成\(yL^*\)

billionaire %>%
  mutate(
    World2=f(World)
  ) -> billionaire

步驟三：設定右Y軸

billionaire %>%
  ggplot()+
  geom_line(
    aes(x=Year,y=Russia), color="blue", size=2
  ) +
  geom_line(
    aes(x=Year,y=World2), color="brown", size=2
  ) + 
  scale_y_continuous(
    limits=c(-1,230),
    breaks=seq(0,200,by=50),
    expand=expand_scale(mult=c(0,0)),
    sec.axis = sec_axis(  # 設定右Y軸
      trans=f_inverse,
      name="Rest of the World"
    )
  ) +
  theme_bw() -> plot_sec_axis 

plot_sec_axis

# 引入theme_dual_axis()
source("https://www.dropbox.com/s/8sdedu4wnq8wsns/guides.R?dl=1")

plot_sec_axis +
  scale_x_continuous(
    limits=c(1995,2015),
    breaks=c(1996,seq(2000,2015,by=5)),
    labels=function(x) ifelse(x<=2000,x,str_sub(as.character(x),3,4))
  )+
  labs(x="",y="Russia")+
  theme_dual_axis()

6.1.1.2 duplicated axis: dup_axis()

load(url("https://www.dropbox.com/s/r21jg0vxf77geu9/plot_tree.Rda?dl=1"))

plot_tree

plot_tree +
  scale_x_continuous(
    sec.axis = dup_axis()
  ) 

6.1.2 Guides: legend

調整x/y以外aes mapping圖例：

• reference: https://ggplot2.tidyverse.org/reference/guides.html

+guides(<aes name>=<適當的guide function>)

• 有color bar的使用guid_colorbar()去調整。

  • reference: https://ggplot2.tidyverse.org/reference/guide_colourbar.html

• 其他使用guide_legend()去調整。

  • reference: https://ggplot2.tidyverse.org/reference/guide_legend.html

# 引入p
source("https://www.dropbox.com/s/c6uf71rzxwzoeht/guides.R?dl=1")
p

p + 
  guides(
  color=guide_colorbar(
      title.position = "bottom",
      title.theme=
        element_text(
          color="red"
        ),
      title.hjust=-0.5,
      label.theme=element_text(
        color="blue",
        face="bold",
        size=unit(12,"pt")
      ),
      barheight = unit(0.2,"npc"),
      barwidth = unit(36,"pt"),
      raster=F,
      frame.colour = "brown",
      frame.linewidth = unit(3,"pt"),
      ticks.linewidth = unit(2,"pt"),
      reverse = T,
      direction="vertical"
    ),
  # size="none",
  shape=guide_legend(
    ncol=2,
    title.position = "right",
    reverse = F,
    keywidth = unit(24,"pt"),
    keyheight = unit(24,"pt"),
    label.theme = element_text(
      size=unit(12,"pt")
    ),
    override.aes=list(size=3)
  ),
  size=guide_legend(
    direction = "horizontal"
  )
)+
  labs(
    color='title.theme=element_text\ntitle.position="bottom"\ntitle.hjust=0.5',
    shape="title.position=\"right\""
  )

6.2 Facet

6.2.1 範例

• 取自：作業展示6，作品21 by 林奕齊

load(url("https://github.com/tpemartin/course-108-1-inclass-datavisualization/blob/master/%E4%BD%9C%E5%93%81%E5%B1%95%E7%A4%BA/homework6/graphData_homework6_021.Rda?raw=true"))
source("https://www.dropbox.com/s/0ydtqtxu5guy6i1/theme_lin.R?dl=1")

resume_df %>% 
  mutate(開始 = ymd(開始), 結束 = ymd(結束))  -> resume_df

resume_df %>%
  ggplot(
    aes(x = 開始, y = 項目)) +    
  geom_text(
    aes(label = 名稱), size = 2.5) + 
  geom_segment(
    aes(
      xend = 結束, yend = 項目, color = 分類, size = 2, alpha = 1
      )
    ) +
  scale_x_date(
      breaks = seq(as.Date("2015-01-01"), as.Date("2020-01-01"), by="1 year"),
      labels = scales::date_format("%Y")
      )+
  labs(title = "Kuo, Shih-Jung  郭士榮", subtitle = "熱愛挑戰不設限、豐富國際經驗、在學三份實習") + 
  theme_lin() -> gg_basic

gg_basic

gg_basic +
  facet_grid(分類~.) -> gg_facet

gg_facet

~的表示形式處於soft deprecated，未來要改成：

gg_basic +
  facet_grid(
    rows=vars(分類)
    ) -> gg_facet

gg_facet

• vars(): takes inputs to be evaluated.

要求所有y軸均有相同scale會讓圖面很擠，有些類並不會有某些項目；透過scales修改

6.2.2 Option: scales

• scales: Are scales shared across all facets (the default, “fixed”), or do they vary across rows (“free_x”), columns (“free_y”), or both rows and columns (“free”)?

gg_basic +
  facet_grid(分類~.,  scales = "free_y") -> gg_facet_free

gg_facet_free

gg_facet_free +
  theme(    
    strip.background = element_rect(color = "gray", fill = "#F6F4E8")
    ) 

6.2.3 範例

load(url("https://github.com/tpemartin/course-108-1-inclass-datavisualization/blob/master/%E4%BD%9C%E5%93%81%E5%B1%95%E7%A4%BA/homework3/graphData_homework3_002.Rda?raw=true"))

graphData$sub_2015_city%>%
  arrange(desc(area), avg_nh)%>%
  mutate(city = forcats::fct_inorder(city)) -> df_eldercare

df_eldercare %>%
  ggplot(
    aes(y = avg_nh, x = city, fill = area)
    )+
  geom_col(
    width=0.7
  )+
  coord_flip()+
  labs(x = "長照機構數(每10,000位老人)", y="")+
  theme_lin() -> gg_original

gg_original

gg_original+
  facet_grid(
    rows=vars(area), scales="free_y"
  )

6.2.4 Option: space

• If “free_y” their height will be proportional to the length of the y scale; if “free_x” their width will be proportional to the length of the x scale; or if “free” both height and width will vary.

gg_original+
  facet_grid(
    rows=vars(area), scales="free_y", space="free_y"
  )

6.3 Theme

任何ggplot都會有一個預設的theme（全部ggplot2 themes）, 內定為theme_grey()，接著可以透過theme()去改設定：

• which component?

• how to set its value?

  • atomic vector.

  • list: involved with a lot of settings. usually via some other functions, such as:

    • element_text/line/rect() or element_blank()

    • unit()

    • margin()

6.3.1 Component: plot

• (*)會造成plot.margin 之margin(t,l)的增加，因文字的hjust=1,vjust=0（即文字塊的右下角為座標點）。若再配會plot.tag.position=c(0,1)，則tag文字會消失。

6.3.2 Component: legend

6.4 Size

6.4.1 grid::unit()

透過此函數計算較容易：

unit(<數字>,<單位>)

單位：

6.4.2 npc / snpc

• 以整個圖面width/height為衡量長度，1為全圖面width/height。

• npc: 以尺度所用之處為width或height, 相對於圖面full width或full height。

• snpc: 相對於相對於圖面的min{full width, full height}，即Viewport的短邊。

dat <- data.frame(
  x = 1:5, 
  y = 1:5, 
  size = 8+1:5, 
  q = factor(1:5), 
  r = factor(1:5),
  lineheight=seq(0.5,1.5,length.out = 5))

p <- ggplot(
  dat, 
  aes(x, y, 
      colour = size)) +
  geom_point()+
  geom_line()

p+
  theme(
    plot.background = element_rect(
      fill="aliceblue"),
    panel.background = element_rect(
      fill="transparent"
    )
  ) -> p_npc0

source("https://www.dropbox.com/s/3ejnr4sogfvguep/theme_size.R?dl=1")
p_npc0

p_npc0 +
  guides(
    color=guide_colorbar(
      barheight = unit(.5,"npc") # Viewport height的50% (即0.5) 
    )
  )

p_npc0 +
  theme(
    legend.position = "top"
  ) -> p_npc0_top

p_npc0_top +
  guides(
    color=guide_colorbar(
      barwidth = unit(1,"npc") # Viewport width的100%
    )
  ) -> p_unit_npc

p_unit_npc+
  labs(
    title="barwidth=1 npc"
  )

p_npc0_top +
  guides(
    color=guide_colorbar(
      barwidth = unit(1,"snpc") # Viewport 短邊(即height)的100%
    )
  ) -> p_unit_snpc
p_unit_snpc+
  labs(
    title="barwidth=1 snpc"
  )

6.4.3 pt

• 字體多以此為單位。

• 圖面的基本font size即base_size=11（見https://ggplot2.tidyverse.org/reference/ggtheme.html）

• 不同地方的size單位不同，要細讀說明：

  • geom_text: size 1 = 1 mm

  • element_text: size 1 = 1 pt

  • 1 mm / .pt = 1 pt

p_npc0+
  geom_text(
    aes(label=size,size=I(size/.pt)), # /.pt讓值為pt值
    vjust=0, nudge_y=0.1
  )+
  theme_grey(
    base_size=11,
  )+
  theme(
    legend.position = "top",
  ) -> p_base11

p_base11 + 
  guides(
    color=guide_colorbar(
      label.theme = element_text(
        size=11
      ),
      title.theme = element_text(
        size=11
      ),
      barwidth = unit(1,"snpc")
    ),
    size="none"
  )+
  labs(
    title="colorbar title及label均為11 pts"
  )

6.4.4 lines

• 字體行高。以base_size為1。

p_npc0+
  geom_text(
    aes(label=size,size=I(size/.pt)), # /.pt讓值為pt值
    vjust=0, nudge_y=0.1
  )+
  theme_grey(
    base_size=11,
  )+
  theme(
    legend.position = "top",
  ) -> p_base11

p_base11+
  guides(
    color=guide_colorbar(
      title.theme = element_text(size=11),
      barwidth = unit(5,"lines")
    )
  )

6.4.5 Guidelines

• 字體以pt為主，並相對於base_size。

• 非文字配置，視所要感受：

  • 相對於所要對應之字體

  • 相對於viewport

6.5 Customize your graph

• 4.5 The grid package, from Mastering Software Development in R:

  • Especially, 4.5.5 The gridExtra package