四，标记与线形

绘图中的标记由pch参数来节制。其描边色由col节制，填充色由bg节制。

> pchShow <-
+   function(extras = c("*",".", "o","O","0","+","-","|","%","#"),
+            cex = 3, ## good for both .Device=="postscript" and "x11"
+            col = "red3", bg = "gold", coltext = "brown", cextext = 1.2,
+            main = paste("plot symbols :  points (...  pch = *, cex =",
+                         cex,")"))
+   {
+     nex <- length(extras)
+     np  <- 26 + nex
+     ipch <- 0:(np-1)
+     k <- floor(sqrt(np))
+     dd <- c(-1,1)/2
+     rx <- dd + range(ix <- ipch %/% k)
+     ry <- dd + range(iy <- 3 + (k-1)- ipch %% k)
+     pch <- as.list(ipch) # list with integers & strings
+     if(nex > 0) pch[26+ 1:nex] <- as.list(extras)
+     plot(rx, ry, type="n", axes = FALSE, xlab = "", ylab = "",
+          main = main)
+     abline(v = ix, h = iy, col = "lightgray", lty = "dotted")
+     for(i in 1:np) {
+       pc <- pch[[i]]
+       ## 'col' symbols with a 'bg'-colored interior (where available) :
+       points(ix[i], iy[i], pch = pc, col = col, bg = bg, cex = cex)
+       if(cextext > 0)
+           text(ix[i] - 0.3, iy[i], pc, col = coltext, cex = cextext)
+     }
+   }
> 
> pchShow()

标记

线形主要由lty和lwd来节制。lty: line type. lwd: line width.顾名思意，lty节制线的形状，而lwd节制线的粗细，默认值为1。设计成2暗示两倍线宽。

线形

五，坐标轴，图例，标志与标题

相关参数来节制，它们有

增加一个新的坐标轴利用axis()函数。

> # A Silly Axis Example
> 
> # specify the data 
> x <- c(1:10); y <- x; z <- 10/x
> 
> # create extra margin room on the right for an axis 
> par(mar=c(5, 4, 4, 8) + 0.1)
> 
> # plot x vs. y 
> plot(x, y,type="b", pch=21, col="red", 
+    yaxt="n", lty=3, xlab="", ylab="")
> 
> # add x vs. 1/x 
> lines(x, z, type="b", pch=22, col="blue", lty=2)
> 
> # draw an axis on the left 
> axis(2, at=x,labels=x, col.axis="red", las=2)
> 
> # draw an axis on the right, with smaller text and ticks 
> axis(4, at=z,labels=round(z,digits=2),
+   col.axis="blue", las=2, cex.axis=0.7, tck=-.01)
> 
> # add a title for the right axis 
> mtext("y=1/x", side=4, line=3, cex.lab=1,las=2, col="blue")
> 
> # add a main title and bottom and left axis labels 
> title("An Example of Creative Axes", xlab="X values",
+    ylab="Y=X")

坐标轴

图例利用legend()函数节制

> attach(mtcars)
> boxplot(mpg~cyl, main="Milage by Car Weight",
+   	 yaxt="n", xlab="Milage", horizontal=TRUE,
+    col=terrain.colors(3))
> legend("topright", inset=.05, title="Number of Cylinders",
+   	 c("4","6","8"), fill=terrain.colors(3), horiz=TRUE)

图例

文本框利用text可能mtext函数。text可以在主画图区内加文本框，mtext在边距可能外边距上加文本框。

#p#分页标题#e#

text(location, “text to place”, pos, …)
mtext(“text to place”, side, line=n, …)

> attach(mtcars)
> plot(wt, mpg, main="Milage vs. Car Weight", 
+   	 xlab="Weight", ylab="Mileage", pch=18, col="blue")
> text(wt, mpg, row.names(mtcars), cex=0.6, pos=4, col="red")

文本框

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