如何用Stata的graph命令绘制双柱状图和折线图的组合

可以使用Stata的`graph twoway`命令来绘制双柱状图和折线图的组合。下面是一个示例代码：

sysuse auto, clear
graph twoway (bar mpg weight, barwidth(0.4) barlabel(foreground(white))) ///
(line price, yaxis(2) lcolor(blue) lpattern(dash)) ///
legend(order(1 "MPG" 2 "Weight" 3 "Price") region(color(white))) ///
ytitle("MPG and Weight" "Price") xtitle("Car Model") ///
title("MPG, Weight and Price by Car Model") ///
scheme(s1color)

上述代码中，`graph twoway`命令用于绘制双柱状图和折线图的组合。其中，`(bar mpg weight, barwidth(0.4) barlabel(foreground(white)))`用于绘制双柱状图，`barwidth(0.4)`参数指定柱子宽度为0.4，`barlabel(foreground(white))`参数指定柱子标签颜色为白色；`(line price, yaxis(2) lcolor(blue) lpattern(dash))`用于绘制折线图，`yaxis(2)`参数指定折线图使用右侧的y轴，`lcolor(blue)`参数指定折线颜色为蓝色，`lpattern(dash)`参数指定折线类型为虚线。`legend(order(1 "MPG" 2 "Weight" 3 "Price") region(color(white)))`用于设置图例，`order(1 "MPG" 2 "Weight" 3 "Price")`参数指定图例中条目的顺序和标签，`region(color(white))`参数指定图例背景颜色为白色。`ytitle("MPG and Weight" "Price")`用于设置y轴标题，`xtitle("Car Model")`用于设置x轴标题，`title("MPG, Weight and Price by Car Model")`用于设置图表标题，`scheme(s1color)`用于设置图表样式。