计算直线与水平轴之间的角度

Question

请考虑以下玩具数据集：

clear
input double(x y)
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end

现在考虑以下图形：

twoway line y x || scatteri 0 0 "Line A", msymbol(none) msymbol(none) /// 
mlabgap(0) mlabposition(0) mlabangle(60) legend(off)

很明显，直线A相对于x-axis的角度为60度（手动指定）：

我尝试按照在similar post中找到的建议来计算该角度：

summarize y
scalar y1 = r(min)
scalar y2 = r(max)

summarize x
scalar x1 = r(min)
scalar x2 = r(max)

scalar dy = y2 - y1
scalar dx = x2 - x1

display (180 / _pi) * atan2(dy, dx)
89.990983

为什么Stata生成的角度为60而不是90度的图形？

如果我将图形的长宽比设置为1，则角度似乎会更改为68，但仍远不接近计算值：

twoway line y x || scatteri 0 0 "Line A", msymbol(none) msymbol(none) /// 
mlabgap(0) mlabposition(0) mlabangle(68) legend(off) aspectratio(1)

考虑到比例和长宽比的差异，如何连续计算角度？

Answer 1

x和y轴在图中的比例不同，因此这不是1：1的纵横比，并且绘制的许多角度将与等轴比例下的预期角度不同。 这是几个图形包中的默认设置，因为它通常可以更好地在图形中散布数据。