R语言ggplot2包之坐标轴详解

library(ggplot2)
library(gcookbook)
ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot()
ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot() + coord_flip()

#因子坐标轴
ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot() + coord_flip() +
scale_x_discrete(limits=rev(levels(PlantGrowth$group)))
#连续变量的逆转
ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot() + scale_y_reverse()
#改变分类变量顺序
ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot()+scale_x_discrete(limits=c("trt1","ctrl","trt2"))

p <- ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot()
p + ylim(0, max(PlantGrowth$weight))
#ylim()是对scale_y_continuous()的快速实现。
#其中breaks用来控制刻度。
p + scale_y_continuous(limits=c(0, 10), breaks=NULL)

sp <- ggplot(marathon, aes(x=Half,y=Full)) + geom_point()
#1:1
sp + coord_fixed() +
scale_y_continuous(breaks=seq(0, 420, 30)) +
scale_x_continuous(breaks=seq(0, 420, 30))
#1:2 x轴刻度长度比y轴刻度长度
sp + coord_fixed(ratio=1/2) +
scale_y_continuous(breaks=seq(0, 420, 30)) +
scale_x_continuous(breaks=seq(0, 420, 15))

#连续变量
ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot() +
scale_y_continuous(breaks=c(4, 4.25, 4.5, 5, 6, 8))
#看到没有，刻度线位置已经按照breaks设置的参数改变了
#如果是离散变量，则使用scale_x_discrete函数
#通过limit函数来控制标签的个数和顺序
ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot() +
scale_x_discrete(limits=c("trt2", "ctrl"))

p <- ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot()
#去除刻度标签
p + theme(axis.text.y = element_blank())
#去除刻度线
p + theme(axis.ticks.y = element_blank(), axis.text.y = element_blank())
#去除网格线
p + scale_y_continuous(breaks=NULL)

hwp <- ggplot(heightweight, aes(x=ageYear, y=heightIn)) +
geom_point()
hwp + scale_y_continuous(breaks=c(50, 56, 60, 66, 72),
labels=c("Tiny", "Really\nshort", "Short",
"Medium", "Tallish"))
#值得注意的是，若标签太长，可以用\n将文本放到下一行进行显示

bp <- ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot() +
scale_x_discrete(breaks=c("ctrl", "trt1", "trt2"),
labels=c("Control", "Treatment 1", "Treatment 2"))
#垂直显示
bp + theme(axis.text.x = element_text(angle=90, hjust=1, vjust=.5))
#换个角度显示，angle是控制刻度标签显示的角度
bp + theme(axis.text.x = element_text(angle=30, hjust=1, vjust=1))
#hjust和vjust是为了控制刻度标签在水平方向和垂直方向的位置

hwp + xlab("Age in years") + ylab("Height in inches")#hwp在上面例子中已经定义过
#你也可以这么改，两者等价
hwp + labs(x = "Age in years", y = "Height in inches")

hwp+ theme(axis.title.x=element_blank())

hwp + ylab("Height\n(inches)") +
theme(axis.title.y=element_text(angle=90, face="italic", colour="darkred",
size=14))
#这也同样适用于改变刻度线标签的字体、颜色大小。

library(MASS)
p <- ggplot(Animals, aes(x=body, y=brain, label=rownames(Animals))) +
geom_text(size=3)
#只显示标签线
p + scale_x_log10() + scale_y_log10()