我想用viewport垂直合并两个图形。图形是用ggplot和facet_grid()创建的。出现的问题是分类变量的图例长度不同。这会导致图的宽度不同，因为图例占据了更多的位置。我希望图的宽度相同。
我怎样才能解决这个问题？
以下是图未对齐的图形示例：

下面是生成该图的代码：

# dataframe
x <- rep(1:10,2)
y <- x + rep(c(0,2),each=10)
sex <- rep(c("f","m"), each=10)
sex2 <- rep(c("fffffffff","mmmmmmmmm"), each=10)
df0 <- data.frame(x = x, y = y, sex = sex, sex2 = sex2)

# libraries
library("grid")
library("gridExtra")
library("ggplot2")

# Viewport
Layout <- grid.layout(nrow = 2, ncol = 1, heights = unit(c(1,1), c("null","null")))
vplayout <- function(x,y) {
       viewport(layout.pos.row=x, layout.pos.col=y)
}

# plot object
p1 <- ggplot(df0,aes(x = x, y = y,linetype=sex)) +
        geom_line() 

p2 <- ggplot(df0,aes(x = x, y = y,linetype=sex2)) +
        geom_line()         

# figures
tiff("test0.tiff", width=5, height=10, units="cm", res=300, compression = 'lzw')
grid.newpage()
pushViewport(viewport(layout= Layout))
print(p1 +  theme_bw(base_size=5), vp = vplayout(1,1))
print(p2 +  theme_bw(base_size=5), vp = vplayout(2,1))
dev.off()