R语言绘图：test_mse曲线无法显示且无报错问题咨询

Here are practical fixes for your issue where test_mse doesn’t appear on the plot despite no error messages:

• Verify vector length consistency
  Ensure length(test_mse) equals p=10. If the vector is shorter or longer, the points won’t align with the x-axis range 1:p and may fail to render. Run this check:

  length(test_mse) == p
  

• Adjust y-axis range to include test_mse values
  The initial plot() call sets the y-axis bounds based on train_mse values. If test_mse is significantly higher or lower, it’ll be plotted outside the visible area. Update your code to explicitly set a y-axis range that covers both datasets:

  # Calculate combined range of both MSE vectors
  mse_range <- range(c(train_mse, test_mse))
  
  plot(1:p, train_mse, type = "b", pch = 19, col = "blue", 
       xlab = "Number of Components (M)", ylab = "Mean Squared Error (MSE)",
       main = "PCR: Training and Test MSEs vs. Number of Components",
       ylim = mse_range)
  
  points(1:p, test_mse, type = "b", pch = 19, col = "red")
  legend("topright", legend = c("Training MSE", "Test MSE"), col = c("blue", "red"), pch = 19, cex = 0.8)
  

• Check for missing values
  If test_mse contains NA values, those points won’t render. Confirm with:

  any(is.na(test_mse))
  

  If the result is TRUE, handle the missing values (e.g., remove or impute them) before plotting.

• Isolate the issue with simplified code
  To rule out conflicts with the initial plot, try plotting test_mse alone first:

  plot(1:p, test_mse, type="b", col="red")
  

  If this works, the problem was almost certainly the y-axis range in your original plot.

内容的提问来源于stack exchange，提问作者khali-blinks