带有ggplot2的盒装geom_text

Question

我正在用ggplot2开发一个图形,其中我需要在其他图形元素上叠加文本.根据文本底层元素的颜色,可能难以阅读文本.有没有办法在具有半透明背景的边界框中绘制geom_text？

我可以用plotrix做到这一点:

library(plotrix)
Labels <- c("Alabama", "Alaska", "Arizona", "Arkansas")
SampleFrame <- data.frame(X = 1:10, Y = 1:10)
TextFrame <- data.frame(X = 4:7, Y = 4:7, LAB = Labels)
### plotrix ###
plot(SampleFrame, pch = 20, cex = 20)
boxed.labels(TextFrame$X, TextFrame$Y, TextFrame$LAB,
 bg = "#ffffff99", border = FALSE,
 xpad = 3/2, ypad = 3/2)

但我不知道用ggplot2获得类似结果的方法:

### ggplot2 ###
library(ggplot2)
Plot <- ggplot(data = SampleFrame,
 aes(x = X, y = Y)) + geom_point(size = 20)
Plot <- Plot + geom_text(data = TextFrame,
 aes(x = X, y = Y, label = LAB))
print(Plot)

如您所见,黑色文本标签无法感知它们与背景中的黑色geom_points重叠的位置.

Answer 1

试试这个geom,稍微修改一下GeomText.

GeomText2 <- proto(GeomText, {
  objname <- "text2"
  draw <- function(., data, scales, coordinates, ..., parse = FALSE,
                   expand = 1.2, bgcol = "grey50", bgfill = NA, bgalpha = 1) {
    lab <- data$label
    if (parse) {
      lab <- parse(text = lab)
    }

    with(coordinates$transform(data, scales), {
      tg <- do.call("mapply",
        c(function(...) {
            tg <- with(list(...), textGrob(lab, default.units="native", rot=angle, gp=gpar(fontsize=size * .pt)))
            list(w = grobWidth(tg), h = grobHeight(tg))
          }, data))
      gList(rectGrob(x, y,
                     width = do.call(unit.c, tg["w",]) * expand,
                     height = do.call(unit.c, tg["h",]) * expand,
                     gp = gpar(col = alpha(bgcol, bgalpha), fill = alpha(bgfill, bgalpha))),
            .super$draw(., data, scales, coordinates, ..., parse))
    })
  }
})

geom_text2 <- GeomText2$build_accessor()

Labels <- c("Alabama", "Alaska", "Arizona", "Arkansas")
SampleFrame <- data.frame(X = 1:10, Y = 1:10)
TextFrame <- data.frame(X = 4:7, Y = 4:7, LAB = Labels)

Plot <- ggplot(data = SampleFrame, aes(x = X, y = Y)) + geom_point(size = 20)
Plot <- Plot + geom_text2(data = TextFrame, aes(x = X, y = Y, label = LAB),
                          size = 5, expand = 1.5, bgcol = "green", bgfill = "skyblue", bgalpha = 0.8)
print(Plot)

BUG固定和代码改进

GeomText2 <- proto(GeomText, {
  objname <- "text2"
  draw <- function(., data, scales, coordinates, ..., parse = FALSE,
                   expand = 1.2, bgcol = "grey50", bgfill = NA, bgalpha = 1) {
    lab <- data$label
    if (parse) {
      lab <- parse(text = lab)
    }
    with(coordinates$transform(data, scales), {
      sizes <- llply(1:nrow(data),
        function(i) with(data[i, ], {
          grobs <- textGrob(lab[i], default.units="native", rot=angle, gp=gpar(fontsize=size * .pt))
          list(w = grobWidth(grobs), h = grobHeight(grobs))
        }))

      gList(rectGrob(x, y,
                     width = do.call(unit.c, lapply(sizes, "[[", "w")) * expand,
                     height = do.call(unit.c, lapply(sizes, "[[", "h")) * expand,
                     gp = gpar(col = alpha(bgcol, bgalpha), fill = alpha(bgfill, bgalpha))),
            .super$draw(., data, scales, coordinates, ..., parse))
    })
  }
})

geom_text2 <- GeomText2$build_accessor()

Answer 2

而不是添加一个边框的,我建议改变文字颜色为white这可以通过执行来完成

Plot <- Plot + 
  geom_text(data = TextFrame, aes(x = X, y = Y, label = LAB), colour = 'white')

另一种方法是添加一个alphato geom_point以使其更透明

Plot <- Plot + geom_point(size = 20, alpha = 0.5)

编辑.这是一种概括Chase解决方案以自动计算边界框的方法.诀窍是将文本width和height文本直接添加到文本数据框中.这是一个例子

Labels <- c("Alabama", "Alaska", "Arizona", "Arkansas", 
    "Pennsylvania + California")
TextFrame <- data.frame(X = 4:8, Y = 4:8, LAB = Labels)
TextFrame <- transform(TextFrame,
    w = strwidth(LAB, 'inches') + 0.25,
    h = strheight(LAB, 'inches') + 0.25
)

ggplot(data = SampleFrame,aes(x = X, y = Y)) + 
  geom_point(size = 20) +
  geom_rect(data = TextFrame, aes(xmin = X - w/2, xmax = X + w/2, 
    ymin = Y - h/2, ymax = Y + h/2), fill = "grey80") +
  geom_text(data = TextFrame,aes(x = X, y = Y, label = LAB), size = 4)

Answer 3

在ggplot2包的开发版本中,有一个新的geom geom_label(),它直接实现了这个.可以通过alpha=参数来实现Transperency .

ggplot(data = SampleFrame,
       aes(x = X, y = Y)) + geom_point(size = 20)+ 
        geom_label(data = TextFrame,
                         aes(x = X, y = Y, label = LAB),alpha=0.5)

Answer 4

更新ggplot2v0.9

library(ggplot2)
library(proto)

btextGrob <- function (label,x = unit(0.5, "npc"), y = unit(0.5, "npc"), 
    just = "centre", hjust = NULL, vjust = NULL, rot = 0, check.overlap = FALSE, 
    default.units = "npc", name = NULL, gp = gpar(), vp = NULL,  f=1.5) {
    if (!is.unit(x)) 
      x <- unit(x, default.units)
    if (!is.unit(y)) 
      y <- unit(y, default.units)
    grob(label = label, x = x, y = y, just = just, hjust = hjust, 
         vjust = vjust, rot = rot, check.overlap = check.overlap, 
         name = name, gp = gp, vp = vp, cl = "text")
    tg <- textGrob(label = label, x = x, y = y, just = just, hjust = hjust, 
                   vjust = vjust, rot = rot, check.overlap = check.overlap)
    w <- unit(rep(1, length(label)), "strwidth", as.list(label))
    h <- unit(rep(1, length(label)), "strheight", as.list(label))
    rg <- rectGrob(x=x, y=y, width=f*w, height=f*h,
                   gp=gpar(fill="white", alpha=0.3,  col=NA))

    gTree(children=gList(rg, tg), vp=vp, gp=gp, name=name)
  }

GeomText2 <- proto(ggplot2:::GeomText, {
  objname <- "text2"

  draw <- function(., data, scales, coordinates, ..., parse = FALSE, na.rm = FALSE) {
    data <- remove_missing(data, na.rm, 
      c("x", "y", "label"), name = "geom_text2")

    lab <- data$label
    if (parse) {
      lab <- parse(text = lab)
    }

    with(coord_transform(coordinates, data, scales),
      btextGrob(lab, x, y, default.units="native", 
        hjust=hjust, vjust=vjust, rot=angle, 
        gp = gpar(col = alpha(colour, alpha), fontsize = size * .pt,
          fontfamily = family, fontface = fontface, lineheight = lineheight))
    )
  }

})

geom_text2 <- function (mapping = NULL, data = NULL, stat = "identity", position = "identity", 
parse = FALSE,  ...) { 
  GeomText2$new(mapping = mapping, data = data, stat = stat,position = position, 
  parse = parse, ...)
}


qplot(wt, mpg, data = mtcars, label = rownames(mtcars), size = wt) +
   geom_text2(colour = "red")