R 为什么这个表格格罗布不打印

我正在try 将一系列绘图和表格Grob打印到单个PDF文件中.代码执行时没有任何错误，但表不会显示在输出PDF文件中.为什么？我做错什么了？

library(boot)
library(ggplot2)
library(ggblanket)
library(gridExtra)
library(tidyverse)

# define functions to return mean and standard deviation for a given bootstrap sample
fun_mean <- function(data,i){
  d <- data[i]
  return(mean(d, na.rm=TRUE))
}
fun_sd <- function(data,i){
  d <- data[i]
  return(sd(d, na.rm=TRUE))
}

# load the data for each device
mydata <- data.frame(
  Device1 = c(6.3, 8.3, 6.6, 0, 8.4, 8.6),
  Device2 = c(8.2, 8.7, 8.6, 7.9, 7.1, 7.6),
  Device3 = c(7.1, 6.4, 6.6, 8, 7.5, 10.3),
  Device4 = c(8, 7.7, 7.3, 0, 9.4, 6.4),
  Device5 = c(8.5, 6.8, 0, 0, 7.3, 9.7),
  Device6 = c(5.9, 7.5, 6.5, 0, 9.8, 7.8),
  Device7 = c(7.6, 5.3, 6.7, 0, 6.6, 7.4),
  Device8 = c(9.5, 5.6, 8.8, 0, 8.6, 8.3),
  Device9 = c(8.5, 7.4, 0, 0, 9.2, 8.6),
  Device10 = c(7.8, 6.9, 8.6, 6.7, 6.8, 6.1)
)

# Replace all zero values with NA
mydata[mydata == 0] <- NA


# Set number of bootstrap samples
R<- 10000 

# Create a data frame to store results
results_df <- data.frame(
  Device = colnames(mydata),
  Parameter = rep(c("Mean", "S.Dev"), each = ncol(mydata)),
  Num.Resamples = rep(R, 2 * ncol(mydata))
)

# Initialize empty lists to store results for each device
device_results <- list()

# Create a PDF file to output results/plots
pdf("Bootstrap Results.pdf")

# Estimate the bootstrap parameters and export the results
for (i in 1:ncol(mydata)) {
  # Print status to console
  cat(paste("Device", i, "\n"))
  
  # Estimate the bootstrap parameters
  bo_mean <- boot(data = mydata[, i], statistic = fun_mean, R = R)
  bo_sd <- boot(data = mydata[, i], statistic = fun_sd, R = R)
  
  # Obtain confidence intervals for the parameter estimates
  ci_mean <- boot.ci(bo_mean, conf = 0.95, type = "bca")
  ci_sd <- boot.ci(bo_sd, conf = 0.95, type = "bca")
  
  # Store the confidence interval bounds
  ci_mean_bounds <- ci_mean$bca[c(4, 5)]
  ci_sd_bounds <- ci_sd$bca[c(4, 5)]
  
  # Create a histogram for the resamples
  df_mean <- data.frame(samples = bo_mean$t)
  plot_hist <- gg_histogram(
    data = df_mean,
    x = samples
  )
  
  # Create a qq-plot for the resamples
  plot_qq <- gg_qq(
    data = df_mean,
    sample = samples
  ) +
    geom_qq_line(color = "blue")
  
  # Combine the plots
  plot_combo <- ggarrange(plot_hist, plot_qq,
                          ncol = 2,
                          nrow = 1,
                          widths = c(600, 600),
                          heights = 300)
  
  # Print the combined plot to the PDF file
  print(plot_combo)
  
  # Store the results for the current device
  device_results[[i]] <- data.frame(
    Device = colnames(mydata)[i],
    `Num.Resamples` = R,
    `Mean` = paste(format(bo_mean$t0, nsmall = 5), 
                   " (", format(ci_mean_bounds[1], nsmall = 5), ",", 
                   format(ci_mean_bounds[2], nsmall = 5), ")"),
    `S.Dev` = paste(format(bo_sd$t0, nsmall = 5), 
                    " (", format(ci_sd_bounds[1], nsmall = 5), ",", 
                    format(ci_sd_bounds[2], nsmall = 5), ")")
  )
  
  cat("\n")
}

# Combine the results for all devices into a single data frame
results_df <- bind_rows(device_results)

# Print the results table to the PDF file 
# THIS IS WHAT SEEMS TO BE NOT WORKING 
results_grob <- tableGrob(results_df)
print(results_grob)

# Close the PDF device
dev.off()

# Print the combined table to a text file
write.table(results_df, "Bootstrap Results.txt", row.names = FALSE, quote = FALSE, sep = "\t")