替换gtable中的ggplot元素：标签和网格线 [英] replacing elements of a ggplot inside a gtable: labels and gridlines

问题描述

我正在学习使用 gtable 操作 ggplot 对象。 [这里有一个相关的问题，我问：拆除一个ggplot与网格和gtable ]

现在的问题是：

2. 如何从一个gtable获取各种轴元素，并将它们放入另一个gtable中以替代现有元素？，特别是：替换垂直网格线（以及相应的tickmarks）。
   
   
   

   以下是一些代码和数字。
   
   

    ＃Data 
    df < - 结构（列表（年份= c（1950,2013,1950,2013），国家=结构（c（1L，
    1L，2L，2L），。标签= c（法国 ，美国），class =factor），
    Category = c（小时最低工资，小时最低工资，
   小时最低工资，小时最低工资） ，价值= c（2.14，
    9.43，3.84，7.25），变量= c（法国（2013欧元），
   法国（2013欧元），美国（2013美元） ，Un （2013美元）
   ），单位= c（2013年欧元，2013年欧元，2013美元，2013美元
   ）），.Names = c（ ，Country，Category，value，variable，
   Unit），row.names = c（NA，4L），class =data.frame）
    
   ＃使用ggplot绘制数据
    library（ggplot2）
    p1 < -  ggplot（data = df，aes（x = Year，y = value，group = variable，color = variable，shape =变量））+ 
    geom_line（size = 2，show_guide = FALSE）+ 
    geom_point（size = 4，show_guide = FALSE）+ 
    theme（panel.grid.major.x = element_line （size = 1，color =darkgreen），
    panel.grid.minor.x = element_line（size = 1，color =darkgreen，linetype =dotted））+ 
    theme（ text = element_text（size = 20，color =darkgreen））+ 
    theme（axis.text = element_text（size = 20，color =darkgreen））
     

   以下是p1：
   

   
   

     p2< / p> lt;  -  ggplot（data = df，aes（x = Year，y = value，group = variable，color = variable，shape = variable））+ 
    geom_line（size = 2，show_guide = FALSE）+ 
    geom_point（size = 4，show_guide = FALSE）+ 
    theme（panel.grid.major.x = element_line（size = 1，color =darkred），
    panel.grid.minor。 x = element_line（size = 1，color =darkred，linetype =dotted））+ 
    theme（text = element_text（size = 20，color =darkred））+ 
    theme axis.text = element_text（size = 20，color =darkred））
     

   这是p2：

   
   
   

    ＃将p1的底部轴替换为p2的底部轴
    library（gtable）
    g1 < -  ggplot_gtable（ggplot_build（ p1））
    g2<  -  ggplot_gtable（ggplot_build（p2））
    
   ＃函数从gtables中删除选定的元素，保持宽度
    gtable_grob_remove<  -  function（g，what =guide-box）{
    require（gtable）
   匹配< -c（grepl（pattern = what，g $ layout $ name））
   g $ layout<  -  g $ layout [！matches，drop = FALSE] 
   g $ grobs<  -  g $ grobs [！matches] 
    return（g）
   } 
    
   ＃替换axis-b
   g<  -  g1 
    pos < -  c（子集（g $ layout，name ==axis-b，se = t：r））
   g < -  gtable_grob_remove（g，what =axis-b ）
   g < -  gtable_add_grob（g，g2 $ grobs [[which（g2 $ layout $ name ==axis-b）]]，
    pos $ t，pos $ l，pos $ b ，pos $ r，name =axis-b）
    
   ＃替换xlab
    pos <-c（子集（g $ layout，name ==xlab， （g，g2 $ grobs [[which（g2 $ layout $ name ==））
   g < -  gtable_grob_remove（g，what =xlab）
   g < -  gtable_add_grob xlab）]]，
    pos $ t，pos $ l，pos $ b，pos $ r，，name =xlab）
    
    grid.newpage（）
    grid.draw（g）
     

   以下是p1中的一些p2元素：
   
   

   
   
   g1是绿色的，g2是红色的，我想要红底轴标签和垂直网格线来代替绿色的。
   
   

   我已经成功地识别了轴标签和轴标题，但我仍然在寻找垂直网格线（以及轴标记和轴水平线） ！）。我想他们在面板中，但是如何访问它们并修改它们？

   
   
   

   在之前的评论中， baptiste建议使用名称（ggplotGrob（p2）[[grobs]] [[4]] [[children]]）来识别不同的元素。这将返回：
   
   

     names（ggplotGrob（p2）[[grobs]] [[4]] [[ ]]）
    [1]grill.gTree.843GRID.polyline.828
    [3]geom_point.points.830panel.border.zeroGrob.831
     

   但是，我不知道如何从这里获取。而且，所附的数字，例如.843随着每个会话而改变，所以我想找到一种不硬编码这些数字的方法。感谢您的建议！

   解决方案

   基于其他答案，考虑一下，
   
   

    ＃找到孩子
    grill1<  -  grepl（grill，
    names（g1 [[grobs]] [[4]] [ [children]]））
    grill2<  -  grepl（grill，
    names（g2 [[grobs]] [[4]] [[children]]）） 
    
   ＃交换孩子，父母不会注意到
    g1 [[grobs]] [[4]] [[children]] [grill1]<  -  
    g2 [[grobs]] [[4]] [[children]] [grill2] 
    
    
    grid.newpage（）
    grid.draw （g1）
     

   
   

   I am learning to manipulate ggplot objects with gtable. [Here is a related question I asked: dismantling a ggplot with grid and gtable ]

   The present issue is:

   2. how to take various axis elements from one gtable and place them into another gtable in replacement of existing elements? and in particular: replace the vertical grid lines (and corresponding tickmarks).

   Below some code and figures.

   # Data
   df <- structure(list(Year = c(1950, 2013, 1950, 2013), Country = structure(c(1L, 
   1L, 2L, 2L), .Label = c("France", "United States"), class = "factor"), 
   Category = c("Hourly minimum wage", "Hourly minimum wage", 
   "Hourly minimum wage", "Hourly minimum wage"), value = c(2.14, 
   9.43, 3.84, 7.25), variable = c("France (2013 euros)", 
   "France (2013 euros)", "United States (2013 dollars)", "United States (2013 dollars)"
   ), Unit = c("2013 euros", "2013 euros", "2013 dollars", "2013 dollars"
   )), .Names = c("Year", "Country", "Category", "value", "variable", 
   "Unit"), row.names = c(NA, 4L), class = "data.frame")
   
   # Plot data with ggplot
   library(ggplot2)
   p1 <- ggplot(data = df, aes(x = Year, y = value, group = variable, colour = variable, shape = variable)) + 
   geom_line(size = 2, show_guide = FALSE) + 
   geom_point(size = 4, show_guide = FALSE) +
   theme(panel.grid.major.x = element_line(size = 1, colour = "darkgreen"), 
         panel.grid.minor.x = element_line(size = 1, colour = "darkgreen", linetype = "dotted")) +
   theme(text = element_text(size = 20, colour = "darkgreen")) +
   theme(axis.text = element_text(size = 20, colour = "darkgreen"))
   

   Here is p1:

   p2 <- ggplot(data = df, aes(x = Year, y = value, group = variable, colour = variable, shape = variable)) + 
   geom_line(size = 2, show_guide = FALSE) + 
   geom_point(size = 4, show_guide = FALSE) +
   theme(panel.grid.major.x = element_line(size = 1, colour = "darkred"), 
         panel.grid.minor.x = element_line(size = 1, colour = "darkred", linetype = "dotted")) +
   theme(text = element_text(size = 20, colour = "darkred")) +
   theme(axis.text = element_text(size = 20, colour = "darkred"))
   

   Here is p2:

   # replace the bottom axis of p1 with that of p2
   library(gtable)
   g1 <- ggplot_gtable(ggplot_build(p1))
   g2 <- ggplot_gtable(ggplot_build(p2))
   
   # function to remove selected elements from gtables, keeping widths
   gtable_grob_remove <- function (g, what = "guide-box") {
       require(gtable)
       matches <- c(grepl(pattern = what, g$layout$name))
       g$layout <- g$layout[!matches, , drop = FALSE]
       g$grobs <- g$grobs[!matches]
       return(g)
   }
   
   # replace "axis-b"
   g <- g1
   pos <- c(subset(g$layout, name == "axis-b", se = t:r))
   g <- gtable_grob_remove(g, what = "axis-b")
   g <- gtable_add_grob(g, g2$grobs[[which(g2$layout$name == "axis-b")]], 
       pos$t, pos$l, pos$b, pos$r, , name = "axis-b")
   
   # replace "xlab"
   pos <- c(subset(g$layout, name == "xlab", se = t:r))
   g <- gtable_grob_remove(g, what = "xlab")
   g <- gtable_add_grob(g, g2$grobs[[which(g2$layout$name == "xlab")]], 
       pos$t, pos$l, pos$b, pos$r, , name = "xlab")
   
   grid.newpage()
   grid.draw(g)
   

   Here is p1 with some p2 elements:

   g1 is green, g2 is red, I want the red bottom axis labels and vertical grid lines to replace the green ones.

   I have been successful in identifying the axis labels and axis title, but I'm still looking for the vertical grid lines (and the axis tickmarks and the axis horizontal line too!). I imagine they are inside the panel, but how to access them and alter them?

   In a previous comment, baptiste suggested names(ggplotGrob(p2)[["grobs"]][[4]][["children"]]) as a way to identify different elements. This returns:

   names(ggplotGrob(p2)[["grobs"]][[4]][["children"]])
   [1] "grill.gTree.843"           "GRID.polyline.828"        
   [3] "geom_point.points.830"     "panel.border.zeroGrob.831"
   

   However, I do not know how to take it from here. Also, the appended numbers, e.g. .843 change with every session, so I would like to find a way to not hardcode these numbers. Thanks for suggestions!

   解决方案

   based on the other answer, consider this,

   # locate the children
   grill1 <- grepl("grill", 
                 names(g1[["grobs"]][[4]][["children"]]))
   grill2 <- grepl("grill", 
                   names(g2[["grobs"]][[4]][["children"]]))
   
   # swap the kids, the parents won't notice
   g1[["grobs"]][[4]][["children"]][grill1] <- 
     g2[["grobs"]][[4]][["children"]][grill2]
   
   
   grid.newpage()
   grid.draw(g1)
   

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