The book and the graph you cited are older version of qplot. Modern version of qplot does not even have binwidth option. Your output is correct, even Excel plot histogram like your output. Don't worry about qplot. Here is qplot format: qplot(x, y, data=, color=, shape=, size=, alpha=, geom=, method=, formula=, facets=, xlim=, ylim= xlab=, ylab=, main=, sub=), not binwidth! You should focus more on ggplot2, not the simple version qplot. Happy learning!

Really helpful,  Thanks.  I should change my learning method that I always struggle on some little point and cannot move on for couple of days.
Thanks for your help.

这个应该是第一个区间左边的值问题，从你的现象来看，以前的版本应该是将左边的值设定为数值的最小值，而现在的版本则是设为最小值再减去0.5，一个比最小值更小的值

对啊，感觉就是怪怪的~~容易让人confused

说实在ggplot2画直方图真的很丑，反而hist()画出来的更简洁点。