在R中用渐变比例填充多边形

我想创建一个仪表来可视化一个变量对另一个变量是否有或多或少的影响。

我构建了一个函数来绘制仪表，并用 3 种不同的颜色填充它。

gg.gauge <- function(pos,breaks=c(0,33,66,100),determinent) {

  require(ggplot2)

  get.poly <- function(a,b,r1=0.5,r2=1.0) {
    th.start <- pi*(1-a/100)
    th.end   <- pi*(1-b/100)
    th       <- seq(th.start,th.end,length=100)
    x        <- c(r1*cos(th),rev(r2*cos(th)))
    y        <- c(r1*sin(th),rev(r2*sin(th)))
    return(data.frame(x,y))
  }
  
  ggplot()+ 
    geom_polygon(data=get.poly(breaks[1],breaks[2]),aes(x,y), fill = "red")+
    geom_polygon(data=get.poly(breaks[2],breaks[3]),aes(x,y), fill = "gold")+
    geom_polygon(data=get.poly(breaks[3],breaks[4]),aes(x,y), fill = "green")+
    geom_polygon(data=get.poly(pos-1,pos+1,0.2),aes(x,y))+
    geom_text(data=as.data.frame(breaks), size=5, fontface="bold", vjust=0,
              aes(x=0.8*cos(pi*(1-    breaks/100)),y=-0.1),label=c('Less','','',"More"))+
        annotate("text",x=0,y=0,label=determinent,vjust=0,size=8,fontface="bold")+
    coord_fixed()+
    theme_bw()+
    theme(axis.text=element_blank(),
          axis.title=element_blank(),
          axis.ticks=element_blank(),
          panel.grid=element_blank(),
          panel.border=element_blank(),
          legend.position = "none") 
}

Output:

我想用渐变颜色填充，这样它就能产生从红色（低）到绿色（高）的褪色效果，而不会产生非常明显的剪切。

我尝试使用scale_fill_grdientn没有积极的结果。

Thanks

实现此目的的最简单方法是使用单独的线段而不是多边形。以下面的修改示例为例，我只更改了定义get_poly并使用geom_segment代替geom_polygon:

gg.gauge <- function(pos, breaks = c(0, 33, 66, 100), determinent) {
  require(ggplot2)
  get.poly <- function(a, b, r1 = 0.5, r2 = 1.0) {
    th.start <- pi * (1 - a / 100)
    th.end   <- pi * (1 - b / 100)
    th       <- seq(th.start, th.end, length = 1000)
    x        <- r1 * cos(th)
    xend     <- r2 * cos(th)
    y        <- r1 * sin(th)
    yend     <- r2 * sin(th)
    data.frame(x, y, xend, yend)
  }

  ggplot() + 
    geom_segment(data = get.poly(breaks[1],breaks[4]), 
                 aes(x = x, y = y, xend = xend, yend = yend, color = xend)) +
    scale_color_gradientn(colors = c("red", "gold", "green")) +
    geom_segment(data = get.poly(pos - 1, pos + 1, 0.2), aes(x = x, y  =y, xend = xend, yend = yend)) +
    geom_text(data=as.data.frame(breaks), size = 5, fontface = "bold", vjust = 0,
              aes(x = 0.8 * cos(pi * (1 - breaks / 100)),  y = -0.1), label = c('Less', '', '', "More")) +
    annotate("text", x  = 0, y = 0,label=determinent,vjust=0,size=8,fontface="bold")+
    coord_fixed()+
    theme_bw()+
    theme(axis.text=element_blank(),
          axis.title=element_blank(),
          axis.ticks=element_blank(),
          panel.grid=element_blank(),
          panel.border=element_blank(),
          legend.position = "none")
}
gg.gauge(pos = 10, determinent = "Test")