【1.7】坐标中断(axis breaks)-- plotrix

R当中的坐标中断一般都使用plotrix库中的axis.break(), gap.plot(), gap.barplot(), gap.boxplot()等几个函数来实现，例：

axis.break

> install.packages("plotrix")
> library(plotrix)
> opar<-par(mfrow=c(3,2))  #将画板分区
> plot(sample(5:7,20,replace=T),main="A ",ylim=c(2,8))
> axis.break(axis=2,breakpos=2.5,style="gap")
> plot(sample(5:7,20,replace=T),main="B",ylim=c(2,8))
> axis.break(axis=2,breakpos=3.5,style="slash")
#> plot(sample(5:7,20,replace=T),main="各个 ",ylim=c(2,8))
#> axis.break(axis=2,breakpos=4.5,style="zigzag")

help(axis.break)

axis.break(axis=1,breakpos=NULL,pos=NA,bgcol="white",breakcol="black",
  style="slash",brw=0.02)

axis：      which axis to break
breakpos         ：where to place the break in user units
pos：      position of the axis (see axis)
bgcol：   the color of the plot background
breakcol：      the color of the "break" marker
style         ：  Either gap, slash or zigzag
brw：      break width relative to plot width

gap.plot

twogrp<-c(rnorm(5)+4,rnorm(5)+20,rnorm(5)+5,rnorm(5)+22);
gpcol<-c(2,2,2,2,2,3,3,3,3,3,4,4,4,4,4,5,5,5,5,5);
gap.plot(twogrp,gap=c(8,16),xlab="Index",ylab="Group values", main="E ",col=gpcol);
gap.plot(twogrp,rnorm(20),gap=c(8,16),gap.axis="x",xlab="Xvalues",xtics=c(4,7,17,20),ylab="Y values",main="D");

help(gap.plot)

gap.plot(x,y,gap,gap.axis="y",bgcol="white",breakcol="black",brw=0.02,xlim=range(x),ylim=range(y),xticlab,xtics=NA,yticlab,ytics=NA,lty=rep(1,length(x)),col=rep(par("col"),length(x)),pch=rep(1,length(x)),add=FALSE,stax=FALSE,...)

x,y:    data values
gap:   the range(s) of values to be left out  省略的轴
gap.axis:   whether the gaps are to be on the x or y axis   在哪个轴上省略
bgcol:       the color of the plot background
breakcol:  the color of the "break" marker
brw:         break width relative to plot width
xlim,ylim:         the plot limits.
xticlab:    labels for the x axis ticks
xtics          :  position of the x axis ticks  #x轴显示的表号
yticlab:    labels for the y axis ticks
ytics          :  position of the y axis ticks
lty:     line type(s) to use if there are lines
col:  color(s) in which to plot the values
pch:   symbols to use in plotting.
add:            whether to add values to an existing plot.
stax:           whether to call staxlab for staggered axis labels.

gap.barplot

#> gap.barplot(twogrp,gap=c(8,16),xlab="Index",ytics=c(3,6,17,20),ylab="Group values",main="F")
> gap.barplot(twogrp,gap=c(8,16),xlab="Index",ytics=c(3,6,17,20),ylab="Group values",horiz=TRUE,main="E")
> twovec<-list(vec1=c(rnorm(30),-6),vec2=c(sample(1:10,40,TRUE),20))
>  gap.boxplot(twovec,gap=list(top=c(12,18),bottom=c(-5,-3)),main="F")
> gap.boxplot(twovec,gap=list(top=c(12,18),bottom=c(-5,-3)),range=0,main="Include outliers in whiskers")
> par(opar)  #关闭当前，返回上一次的画板

从图像效果上来看，这样的坐标中断只能说实现了坐标中断，但效果上是非常一般的。甚至远不如excel, openoffice当中出图效果好。为此，我们需要对plotrix库中的gap.plot做出修改，以达到满意的效果。

最简单的修改办法就是在使用了gap.plot, gap.barplot, gap.boxplot之后重新使用axis.break来修改中断类型，使得看上去美一点。

> axis.break(2,from,breakcol="snow",style="gap")
> axis.break(2,from*(1+0.02),breakcol="black",style="slash")
> axis.break(4,from*(1+0.02),breakcol="black",style="slash")
> axis(2,at=from)

使用上面的办法可以绘制出双反斜线中断，并可以视实际情况加油断点起止位置。

改进的gap.plot

> library(plotrix)
> x<-c(1:5,6.9,7)
> y<-2^x
> from<-33
> to<-110
> opar<-par(mfrow=c(2,2))
>plot(x,y,type="b",main="normal plot")

> gap.plot(x,y,gap=c(from,to),type="b",main="gap plot")
> axis.break(2,from,breakcol="snow",style="gap")
> axis.break(2,from*(1+0.02),breakcol="black",style="slash")
> axis.break(4,from*(1+0.02),breakcol="black",style="slash")
> axis(2,at=from)

> gap.barplot(y,gap=c(from,to),col=as.numeric(x),main="barplot with gap")
> axis.break(2,from,breakcol="snow",style="gap")
> axis.break(2,from*(1+0.02),breakcol="black",style="slash")
> axis.break(4,from*(1+0.02),breakcol="black",style="slash")
> axis(2,at=from)

> gap.barplot(y,gap=c(from,to),col=as.numeric(x),horiz=T,main="Horizontal barplot with gap")
> axis.break(1,from,breakcol="snow",style="gap")
> axis.break(1,from*(1+0.02),breakcol="black",style="slash")
> axis.break(3,from*(1+0.02),breakcol="black",style="slash")
> axis(1,at=from)
> par(opar)

参考资料：

http://www.dataguru.cn/article-4827-1.html