R-如何将图例标题添加到保存到变量的levelplot？

我想在保存到变量的levelplot图中添加图例的标题

例如，此代码可以工作：

library(lattice)
library(grid)
x = 1:10
y = rep(x,rep(10,10))
x = rep(x,rep(10))
z = x+y  
levelplot(z~x*y, colorkey=list(labels=list(cex=1,font=2,col="brown"),height=1,width=1.4),main=list('b',side=1,line=0.5))
trellis.focus("legend", side="right", clipp.off=TRUE, highlight=FALSE)
grid.text(expression(m^3/m^3), 0.2, 0, hjust=0.5, vjust=1)
trellis.unfocus()

但是，如果将同一绘图另存为变量，则此代码不起作用：

p1 <- levelplot(z~x*y, colorkey=list(labels=list(cex=1,font=2,col="brown"),height=1,width=1.4),main=list('b',side=1,line=0.5))
trellis.focus("legend", side="right", clipp.off=TRUE, highlight=FALSE)
grid.text(expression(m^3/m^3), 0.2, 0, hjust=0.5, vjust=1)
trellis.unfocus()

---

p1这不会直接回答您的问题，但它可能会改变工作流程，您可以使用colorkey参数为密钥添加标题

它涉及调整
draw.colorkey
函数

最简单的方法是交互使用
fixInNamespace

fixInNamespace("draw.colorkey", "lattice")

在函数末尾，将最后几行更改为

    }
    if (!is.null(key$title)) {
        key.gf <- placeGrob(key.gf, textGrob(key$title, hjust = key$hjust, 
            vjust = key$vjust, gp = key$gp), row = key$row, col = key$column)
    }
    if (draw) 
        grid.draw(key.gf)
    key.gf
}

}
如果（！为.null（键$title））{
key.gf看起来简单多了
library(lattice)
library(grid)

# Amend key function
# Hopefully a nicer way to do this!
mykey <- draw.colorkey

body(mykey)[28:30] <- list(
quote(
  if(!is.null(key$title)){
      key.gf <- placeGrob(key.gf,
                      textGrob(key$title,hjust=key$hjust, vjust=key$vjust, gp=key$gp),
                          row=key$row, col=key$column)
  }),
body(mykey)[[28]], 
body(mykey)[[29]])

# Assign to namespace: http://stackoverflow.com/questions/6254744/override-a-function-that-is-imported-in-a-namespace
unlockBinding("draw.colorkey", as.environment("package:lattice"))
assign("draw.colorkey", mykey, "package:lattice")
unlockBinding("draw.colorkey", getNamespace("lattice"))
assign("draw.colorkey", mykey, getNamespace("lattice"))

# Draw plot
x = 1:10
y = rep(x,rep(10,10))
x = rep(x,rep(10))
z = x+y 
p <- levelplot(z~x*y, 
              colorkey=list(labels=list(cex=1, font=2, col="brown"),
                            height=1, width=1.4,
                            title=expression(m^3/m^3), row=3, column=1, vjust=2),
               main=list('b',side=1,line=0.5))


p