如何将图例添加到用 lattice 和 latticeExtra 制作的绘图中？

Question

我使用 lattice 和 lattice extra 绘制了五个不同区域的观察值和预测值。我使用 xyplot 绘制观察值，然后使用 lattice extra 中的 as.layer 函数添加预测线。我想在图表中添加图例，但没有成功。

这里有两个示例数据集以及绘图代码。

示例数据集一。我只包括两个领域。

example1 <- 
structure(list(model_predict = c(10, 25, 95, 23, 56, 70, 56, 
45, 25, 50), Shell_Height = c(27, 33, 115, 25, 46, 50, 35, 35, 
23, 45), SAMS_region_2015 = structure(c(1L, 1L, 1L, 1L, 1L, 2L, 
2L, 2L, 2L, 2L), .Label = c("DMV", "LI"), class = "factor")), .Names = c("model_predict", 
"Shell_Height", "SAMS_region_2015"), row.names = c(NA, -10L), class = "data.frame")

示例数据集二。也只包括两个区域。

example2 <-
structure(list(Meat_Weight = c(15, 27, 100, 15, 60, 75, 50, 37, 
28, 60), Shell_Height = c(25, 30, 110, 20, 45, 48, 35, 30, 25, 
50), SAMS_region_2015 = structure(c(1L, 1L, 1L, 1L, 1L, 2L, 2L, 
2L, 2L, 2L), .Label = c("DMV", "LI"), class = "factor")), .Names = c("Meat_Weight", 
"Shell_Height", "SAMS_region_2015"), row.names = c(NA, -10L), class = "data.frame")

绘图代码

library(lattice)
library(latticeExtra) 

#observed vs predicted values by SAMS region

foo<-xyplot(Meat_Weight~Shell_Height|SAMS_region_2015,data=example2,
        ylab="Meat Weight (g)",xlab="Shell Height (mm)",type="p",
            col="red",pch=3)

#add layer of observed values

foo <- foo + 
       as.layer(xyplot(model_predict~Shell_Height|SAMS_region_2015,
           type = "l", data = example1, col = "blue", lwd = 4, lty = 3))

我想为图表添加一个图例，其中包含观察和预测文本以及图表中用于不同变量的符号或线条和颜色。

R信息会话信息() R 版本 3.2.1 (2015-06-18) 平台：i386-w64-mingw32/i386（32 位）运行下：Windows 7 x64（内部版本 7601）Service Pack 1

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets 
[7] methods   base     

other attached packages:
 [1] latticeExtra_0.6-26 RColorBrewer_1.1-2  nlme_3.1-120       
 [4] MASS_7.3-40         xlsx_0.5.7          xlsxjars_0.6.1     
 [7] rJava_0.9-6         plyr_1.8.3          RODBC_1.3-12       
[10] lattice_0.20-31    

loaded via a namespace (and not attached):
[1] tools_3.2.1 Rcpp_0.11.6

如有任何帮助，我们将不胜感激。

Answer 1

您可以将 key= 添加到您的两个 xyplot 调用之一

xyplot(Meat_Weight~Shell_Height|SAMS_region_2015,data=example2,
    ylab="Meat Weight (g)",xlab="Shell Height (mm)",type="p",
    col="red",pch=3,
    key=list(columns=2, 
        text=list(lab=c("weight","predict")),
        points=list(pch=c(3,NA), col="red"), 
        lines=list(lty=c(0,3), lwd=4, col="blue"))) + 
as.layer(xyplot(model_predict~Shell_Height|SAMS_region_2015,
    type = "l", data = example1, col = "blue", lwd = 4, lty = 3))

Answer 2

xyplot() 的关键参数采用一个参数列表，可以很好地处理这个问题。唯一真正的技巧是，如果您在列表中包含一个 lines 元素，您可以在 it 中包含一个额外的 type= 元素来指示将绘制哪些项目作为点，作为线。

## Set up a key
foo_key <- list(x = .97, y = .92, corner = c(1, 1),
            text = list(c("Observed", "Predicted")),
            lines = list(type = c("p", "l"), col = c("red", "blue"),
                         pch = 3, lwd = 4, lty = 3))

## Then pass it in to xyplot() via its 'key' argument
foo <- xyplot(Meat_Weight~Shell_Height|SAMS_region_2015,data=example2,
            ylab="Meat Weight (g)",xlab="Shell Height (mm)",
            type = "p", col = "red", pch = 3,
            key = foo_key)
## ... and carry on with your code, adding a layer and printing the whole thing
foo <- foo +
       as.layer(xyplot(model_predict~Shell_Height|SAMS_region_2015,
           type = "l", data = example1, col = "blue", lwd = 4, lty = 3))

foo

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