当我在R内部使用plot（）命令时，在我调整石英窗口大小之前，xlab不会出现。为什么呢？
可重复的例子：
plot(x = c(1,2,3), y = c(1,2,3), xlab = "where are you?")
当我绘制这个时，我没有看到xlab，直到任意调整窗口大小。
我的sessionInfo（）：
> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-apple-darwin10.8.0 (64-bit)
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] grid splines stats graphics grDevices utils
[7] datasets methods base
other attached packages:
[1] pROC_1.5.4 snowfall_1.84-4 snow_0.3-12
[4] glmnet_1.9-5 Matrix_1.0-12 languageR_1.4
[7] e1071_1.6-1 class_7.3-7 caret_5.16-24
[10] reshape2_1.2.2 plyr_1.8 lattice_0.20-15
[13] foreach_1.4.1 cluster_1.14.4 randomForest_4.6-7
[16] neuralnet_1.32 verification_1.35 CircStats_0.2-4
[19] boot_1.3-9 fields_6.8 maps_2.3-2
[22] spam_0.29-3 ROCR_1.0-5 gplots_2.11.3
[25] MASS_7.3-28 KernSmooth_2.23-10 caTools_1.14
[28] gdata_2.13.2 relaxo_0.1-2 quadprog_1.5-5
[31] lasso2_1.2-16 ada_2.0-3 nnet_7.3-7
[34] lars_1.2 rpart_4.1-1 waveslim_1.7.1
[37] gtools_3.0.0 Hmisc_3.12-2 Formula_1.1-1
[40] survival_2.37-4 foreign_0.8-54
loaded via a namespace (and not attached):
[1] bitops_1.0-5 codetools_0.2-8 iterators_1.0.6
[4] stringr_0.6.2 tools_3.0.1