大家经常对ggplot2中的图例不满意，想要各种修改，今天就介绍下图例的各种修改细节，基本上常用的操作都涉及到了！
移除图例
改变图例位置
修改图例的边框和背景
改变图例顺序
反转图例顺序
修改图例标题
修改图例标题外观
移除图例标题
修改图例标签
修改图例标签外观
library(ggplot2)
library(gcookbook)
移除图例
提供3种方法可以在ggplot2中移除图例。
# 基本图形
pg_plot <- ggplot(PlantGrowth, aes(x = group, y = weight, fill = group)) +
geom_boxplot()
pg_plot
plot of chunk unnamed-chunk-2# 首先可以使用guides()函数移除图例
pg_plot +
guides(fill = "none")
然后可以在scale_**函数中移除，这里是fill，你要根据自己的情况换成shape、color等。
pg_plot+scale_fill_discrete(guide = "none")
第3种方法是在theme中移除。
pg_plot+theme(legend.position = "none")
plot of chunk unnamed-chunk-5改变图例位置
也是在theme中更改，
pg_plot <- ggplot(PlantGrowth, aes(x = group, y = weight, fill = group)) +
geom_boxplot() +
scale_fill_brewer(palette = "Pastel2")
pg_plot +
theme(legend.position = "top") # 放在顶部
plot of chunk unnamed-chunk-6legend.position的参数可以是left、right、top、bottom，还可以是坐标。
pg_plot+theme(legend.position = c(0.8,0.3))
plot of chunk unnamed-chunk-7在ggplot2中，左下角的坐标是c(0,0)，右上角的坐标是c(1,1),你可以自己设置想要放置的位置。需要注意的是，你设置的这个坐标是图例中心点的坐标，可以通过legend.justification设置图例的哪个位置放在你的坐标上。
# 图例右下角，放在画布右下角
pg_plot +
theme(legend.position = c(1, 0), legend.justification = c(1, 0))
plot of chunk unnamed-chunk-8p <- ggplot(heightweight, aes(x=ageYear, y=heightIn, shape=sex, colour=sex))+geom_point()
p
plot of chunk unnamed-chunk-9两个图例更改为水平排列：
p + scale_shape_discrete(label = c("female","male")) +
theme(legend.direction = "horizontal")
plot of chunk unnamed-chunk-10修改图例的边框和背景
pg_plot+
theme(legend.position = c(0.85,0.2))+
theme(legend.background = element_rect(fill = "orange",color = "black"))
plot of chunk unnamed-chunk-11中间还有一部分是白色，需要另外一个参数修改：
pg_plot+
theme(legend.position = c(0.85,0.2))+
theme(legend.background = element_rect(fill = "orange",color = "black"),
legend.key = element_rect(fill = "orange")
)
plot of chunk unnamed-chunk-12改变图例顺序
pg_plot <- ggplot(PlantGrowth, aes(x = group, y = weight, fill = group)) +
geom_boxplot()
pg_plot
plot of chunk unnamed-chunk-13# limits
pg_plot +
scale_fill_discrete(limits = c("trt1", "trt2", "ctrl"))
plot of chunk unnamed-chunk-14也可以在画图之前，通过因子化的方法把数据先排好序再画图哦。
反转图例顺序
2种方法。
pg_plot+scale_fill_discrete(guide = guide_legend(reverse = T))
plot of chunk unnamed-chunk-15pg_plot+guides(fill = guide_legend(reverse = T))
plot of chunk unnamed-chunk-16修改图例标题
2种方法。
pg_plot <- ggplot(PlantGrowth, aes(x = group, y = weight, fill = group)) +
geom_boxplot()
pg_plot
labs里面修改
pg_plot + labs(fill = "Condition")
plot of chunk unnamed-chunk-18在scale_*函数里面修改。
pg_plot+scale_fill_discrete(name = "hahah")
plot of chunk unnamed-chunk-19还有一种比较复杂的情况，如果多个一个变量映射给多个图形参数，或者有多个图例，怎么修改呢？像下面这个例子，sex和shape、color都有关。
p <- ggplot(heightweight, aes(x=ageYear, y=heightIn, shape=sex, colour=sex))+geom_point()
p
plot of chunk unnamed-chunk-20可以在scale_*函数中修改：
p + scale_shape_discrete(name = "shape")+
scale_color_discrete(name = "colooorrr")
plot of chunk unnamed-chunk-21也可以在legend中修改：
p + labs(shape = "shapppeee",color = "colooorrr")
plot of chunk unnamed-chunk-22还可以在guides函数中修改：
p + guides(shape = guide_legend(title = "this is\nshape"),
color = guide_legend(title = "cooolor")
)
plot of chunk unnamed-chunk-23修改图例标题外观
pg_plot <- ggplot(PlantGrowth, aes(x = group, y = weight, fill = group)) +
geom_boxplot()
pg_plot
plot of chunk unnamed-chunk-24可以在theme中修改:
pg_plot + theme(
legend.title = element_text(
face = "italic",
family = "Times",
colour = "red",
size = 18
)
)
plot of chunk unnamed-chunk-26也可以在guides中修改：
pg_plot +
guides(fill = guide_legend(title.theme = element_text(
face = "italic",
family = "Times",
colour = "red",
size = 14))
)
plot of chunk unnamed-chunk-27移除图例标题
pg_plot
plot of chunk unnamed-chunk-29可以在theme中修改，也可以在scale_xxx函数中修改，也可以在guides函数中修改。
pg_plot+theme(legend.title = element_blank())
plot of chunk unnamed-chunk-30pg_plot+scale_fill_discrete(name = NULL)
plot of chunk unnamed-chunk-30pg_plot+scale_fill_hue(guide = guide_legend(title = NULL))
plot of chunk unnamed-chunk-30pg_plot+guides(fill = guide_legend(title = NULL))
plot of chunk unnamed-chunk-30修改图例标签
pg_plot
plot of chunk unnamed-chunk-31pg_plot+scale_fill_discrete(labels = c("label1","label2","label3"))
plot of chunk unnamed-chunk-32修改图例标签外观
在theme中修改：
pg_plot +
theme(legend.text = element_text(
colour = "red",
face = "italic",
size = 22)
)
plot of chunk unnamed-chunk-33
