R绘图基础(2)颜色

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计算机保存及还原颜色时有多种方案,较为常用的是两个,RGB和HSV。R预设了657种颜色,可以通过colors()函数调用(或者英式拼写colours())。比如我们常用的红,绿,蓝,

> colors()[c(552,254,26)]
[1] "red"   "green" "blue"

我们可以使用grep来调取我们感兴趣的颜色,

> grep("red",colors())
[1] 100 372 373 374 375 376 476 503 504 505 506 507 524 525 526 527 528 552 553
[20] 554 555 556 641 642 643 644 645
 
> colors()[grep("red",colors())]
[1] "darkred" "indianred" "indianred1" "indianred2" 
[5] "indianred3" "indianred4" "mediumvioletred" "orangered" 
[9] "orangered1" "orangered2" "orangered3" "orangered4" 
[13] "palevioletred" "palevioletred1" "palevioletred2" "palevioletred3" 
[17] "palevioletred4" "red" "red1" "red2" 
[21] "red3" "red4" "violetred" "violetred1" 
[25] "violetred2" "violetred3" "violetred4"
 
> colors()[grep("sky",colors())]
[1] "deepskyblue" "deepskyblue1" "deepskyblue2" "deepskyblue3" 
[5] "deepskyblue4" "lightskyblue" "lightskyblue1" "lightskyblue2"
[9] "lightskyblue3" "lightskyblue4" "skyblue" "skyblue1" 
[13] "skyblue2" "skyblue3" "skyblue4"
 
> SetTextContrastColor <- function(color)
+ {
+   ifelse( mean(col2rgb(color)) > 127, "black", "white")
+ }
> # Define this array of text contrast colors that correponds to each
> # member of the colors() array.
> TextContrastColor <- unlist( lapply(colors(), SetTextContrastColor) )
 
> # 1a. Plot matrix of R colors, in index order, 25 per row.
> # This example plots each row of rectangles one at a time.
> colCount <- 25 # number per row
> rowCount <- 27
> plot( c(1,colCount), c(0,rowCount), type="n", ylab="", xlab="",
+   axes=FALSE, ylim=c(rowCount,0))
> title("R colors")
> 
> for (j in 0:(rowCount-1))
+ {
+   base <- j*colCount
+   remaining <- length(colors()) - base
+   RowSize <- ifelse(remaining < colCount, remaining, colCount)
+   rect((1:RowSize)-0.5,j-0.5, (1:RowSize)+0.5,j+0.5,
+     border="black",
+     col=colors()[base + (1:RowSize)])
+   text((1:RowSize), j, paste(base + (1:RowSize)), cex=0.7,
+     col=TextContrastColor[base + (1:RowSize)])
+ }

R绘图基础(2)颜色

R颜色表

对于大多数理工出身的人来讲,理解颜色并不难,难的是如何选择一种或者多种理想的颜色,让绘图很漂亮。R当中有一个包RColorBrewer就可以为我们解决这个难题,其中预设了很多种颜色组合以供我们使用。

> library(RColorBrewer)
> display.brewer.all()

R绘图基础(2)颜色

RColorBrewer中预设的颜色表

我们看到其中Set3和Paired设定了12种颜色,其余的有多有少,以9种居多。在使用其颜色时,使用brewer.pal(n, name)调用即可,其中n最小值为3最大值为每组预设值数组的长度。比如brewer.pal(12,Paired)

在绘图时,有如下颜色参数

参数 描述
col 绘图使用的颜色,许多函数接受一组颜色,并对不同的数据依次使用颜色。
col.axis 坐标轴字符颜色
col.lab x,y坐标标记颜色
col.main 标题颜色
col.sub 副标题颜色
fg 绘图前景色,包括坐标轴,各类boxes
bg 绘图背景色
> require(graphics)
> par(col.axis="green",col.lab="blue",col.main="darkred",fg="white",bg="black")
> plot(cars,main="speed vs dist")

R绘图基础(2)颜色

颜色设置示例

ybzhao

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