2018-10-18
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ggplot2来实现一页多图
通过构建multiplot函数,能够很容易地做到一页多图,该函数的具体定义附在末尾,如果它并不能完全满足你的需求,可以复制它并在它的基础上进行修改。
首先,构建一系列图像,但不直接去渲染它们,图像的具体细节并不重要,我们只需要将这些图像对象全部存储为变量。
library(ggplot2)
# 下面的例子用到了ggplot2包中自带的示例数据集ChickWeight
# 首先创建图像,第一幅图像——折线图
p1 <- ggplot(ChickWeight, aes(x=Time, y=weight, colour=Diet, group=Chick)) +
geom_line() +
ggtitle("Growth curve for individual chicks")
# 第二幅图像——密度分布图
p2 <- ggplot(ChickWeight, aes(x=Time, y=weight, colour=Diet)) +
geom_point(alpha=.3) +
geom_smooth(alpha=.2, size=1) +
ggtitle("Fitted growth curve per diet")
# 第三幅图像——带拟合线的散点图
p3 <- ggplot(subset(ChickWeight, Time==21), aes(x=weight, colour=Diet)) +
geom_density() +
ggtitle("Final weight, by diet")
# 第四幅图像——分面直方图
p4 <- ggplot(subset(ChickWeight, Time==21), aes(x=weight, fill=Diet)) +
geom_histogram(colour="black", binwidth=50) +
facet_grid(Diet ~ .) +
ggtitle("Final weight, by diet") +
theme(legend.position="none") # 无图例(在这幅图中,图例显得太冗余了)
接下来,我们可以用multiplot函数对创建的图像进行渲染,将它们展示为两行。
multiplot(p1, p2, p3, p4, cols=2)
#> 载入需要grid包
#> geom_smooth: method="auto" and size of largest group is <1000, so using loess. Use 'method = x' to change the smoothing method.
下面是multiplot函数的具体定义,你可以把任意数量的图像名作为其参数,或者构建一个图像列表作为函数中的plotlist。
# Multiple plot function
#
# ggplot objects can be passed in ..., or to plotlist (as a list of ggplot objects)
# - cols: Number of columns in layout
# - layout: A matrix specifying the layout. If present, 'cols' is ignored.
#
# If the layout is something like matrix(c(1,2,3,3), nrow=2, byrow=TRUE),
# then plot 1 will go in the upper left, 2 will go in the upper right, and
# 3 will go all the way across the bottom.
#
multiplot <- function(..., plotlist=NULL, file, cols=1, layout=NULL) {
library(grid)
# Make a list from the ... arguments and plotlist
plots <- c(list(...), plotlist)
numPlots = length(plots)
# If layout is NULL, then use 'cols' to determine layout
if (is.null(layout)) {
# Make the panel
# ncol: Number of columns of plots
# nrow: Number of rows needed, calculated from # of cols
layout <- matrix(seq(1, cols * ceiling(numPlots/cols)),
ncol = cols, nrow = ceiling(numPlots/cols))
}
if (numPlots==1) {
print(plots[[1]])
} else {
# Set up the page
grid.newpage()
pushViewport(viewport(layout = grid.layout(nrow(layout), ncol(layout))))
# Make each plot, in the correct location
for (i in 1:numPlots) {
# Get the i,j matrix positions of the regions that contain this subplot
matchidx <- as.data.frame(which(layout == i, arr.ind = TRUE))
print(plots[[i]], vp = viewport(layout.pos.row = matchidx$row,
layout.pos.col = matchidx$col))
}
}
}
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