疑问（二）

基本信息

sessionInfo()
R version 3.6.1 (2019-07-05)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 18362)

Matrix products: default

locale:
[1] LC_COLLATE=Chinese (Simplified)_China.936  LC_CTYPE=Chinese (Simplified)_China.936   
[3] LC_MONETARY=Chinese (Simplified)_China.936 LC_NUMERIC=C                              
[5] LC_TIME=Chinese (Simplified)_China.936    

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

other attached packages:
[1] Formula_1.2-3     survival_2.44-1.1 lattice_0.20-38   psych_1.8.12      ggplot2_3.2.0    
[6] pacman_0.5.1     

loaded via a namespace (and not attached):
 [1] tidyselect_0.2.5    xfun_0.8            purrr_0.3.2         splines_3.6.1       colorspace_1.4-1   
 [6] htmltools_0.3.6     yaml_2.2.0          base64enc_0.1-3     rlang_0.4.0         pillar_1.4.2          

在运行的过程中出现如下结果

gg <- ggplot(women,aes(x=rownames(women),y=height)) + geom_bar() 
gg
Error: stat_count() must not be used with a y aesthetic.

我又换了一种输入，结果如下：

gg <- ggplot(NULL,aes(x=rownames(women),y=women$height)) + geom_bar() 
gg
Error: stat_count() must not be used with a y aesthetic.

接着，我又换了一种输入，结果如下：

gg <- ggplot(NULL,aes(x=rownames(women))) + geom_bar(aes(y=women$height)) 
gg
Error: stat_count() must not be used with a y aesthetic.

这是为什么呢？下期解答。