如何通过for循环或迭代方法批量绘制xyplot()图形？

我有如下数据集：

df <- structure(list(ID = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), Vid = c(0, 
0, 1, 1, 0, 1, 1, 0, 0, 1), Mus = c(1, 0, 1, 1, 0, 1, 0, 0, 1, 
1), Rea = c(1, 0, 1, 1, 1, 1, 1, 0, 0, 0), Ema = c(1, 0, 0, 1, 
0, 0, 0, 1, 0, 0), SMS = c(1, 0, 1, 1, 0, 0, 0, 0, 0, 0), tel = c(0, 
0, 0, 1, 0, 0, 0, 0, 1, 0), MMT = c(53, 17.5, 48.5, 40, 19.5, 
37.5, 25, 17.5, 22.5, 18.5), rec = c(0.986090887933027, 0.0680321184694875, 
0.968640096476421, 0.865412998525399, 0.100122305069044, 0.802091434784794, 
0.261753760392736, 0.0680321184694875, 0.173118039249657, 0.0826713725018173
), MM_levels = c("HMM", "IMM", "HMM", "IMM", "IMM", "IMM", "IMM", 
"IMM", "IMM", "IMM")), row.names = c(NA, -10L), class = c("tbl_df", 
"tbl", "data.frame"))

尝试用以下for循环批量绘制xyplot()图形：

for(i in names(df[c(2:7,9)])){
  xyplot(x = i,
          y = "rec",
          data = as.data.frame(df),
          necessity = TRUE,
          jitter = TRUE,
          xlab = names(i),
          ylab = "rec")
}

运行无报错但无法生成预期的系列图形，求调整循环或替代方法实现批量绘图。

核心问题分析 #

xyplot属于lattice包的网格图形系统，这类图形在循环中不会自动渲染输出，必须显式调用print()函数才能显示；另外原代码中xlab = names(i)是错误的，i本身就是列名，直接使用i即可。

调整后的for循环代码 #

library(lattice)

# 遍历目标列名
for(i in names(df[c(2:7,9)])){
  # 创建图形对象
  plot_obj <- xyplot(x = i,
                     y = "rec",
                     data = as.data.frame(df),
                     necessity = TRUE,
                     jitter = TRUE,
                     xlab = i,
                     ylab = "rec")
  # 显式打印图形
  print(plot_obj)
}

替代方案：用purrr实现tidy风格批量绘图 #

如果习惯tidyverse工具链，可以用purrr::walk来迭代，自动处理图形打印：

library(lattice)
library(purrr)

# 提取需要绘图的列名
target_columns <- names(df[c(2:7,9)])

# 批量生成并打印图形
walk(target_columns, function(col){
  plot_obj <- xyplot(x = col,
                     y = "rec",
                     data = df,
                     necessity = TRUE,
                     jitter = TRUE,
                     xlab = col,
                     ylab = "rec")
  print(plot_obj)
})

拓展：批量保存图形到文件 #

如果需要将所有图形保存到文件（比如PDF），可以在循环中加入图形设备函数：

library(lattice)

target_columns <- names(df[c(2:7,9)])

# 打开PDF设备，每个图形占一页
pdf("batch_xyplots.pdf", width = 8, height = 6)
for(i in target_columns){
  plot_obj <- xyplot(x = i,
                     y = "rec",
                     data = df,
                     necessity = TRUE,
                     jitter = TRUE,
                     xlab = i,
                     ylab = "rec")
  print(plot_obj)
}
# 关闭设备
dev.off()

内容的提问来源于stack exchange，提问作者12666727b9