Question

我正在尝试将一些Octave代码移植到Java。我正在尝试atan2所以我有以下尝试

octave3.2:53> m1 = [1,2;3,4]
m1 =

   1   2
   3   4

octave3.2:54> m2=[5,6;7,8]
m2 =

   5   6
   7   8

octave3.2:55> atan2(m1,m2)
ans =

   0.19740   0.32175
   0.40489   0.46365

octave3.2:56> atan(1/5)
ans =  0.19740
octave3.2:57> atan(2/6)
ans =  0.32175
octave3.2:58> atan(3/7)
ans =  0.40489
octave3.2:59> atan(4/8)
ans =  0.46365

所以在我看来，atan2以单元格方式应用于第一个参数除以第二个参数的商。我在Java中很好。但是，下面这段代码给出了一些奇怪的东西......

y
x
theta = atan2(y,x)

我得到了类似的痕迹，

y =

  -0.50000  -0.50000  -0.50000  -0.50000  -0.50000  -0.50000  -0.50000  -0.50000  -0.50000  -0.50000
  -0.40000  -0.40000  -0.40000  -0.40000  -0.40000  -0.40000  -0.40000  -0.40000  -0.40000  -0.40000
  -0.30000  -0.30000  -0.30000  -0.30000  -0.30000  -0.30000  -0.30000  -0.30000  -0.30000  -0.30000
  -0.20000  -0.20000  -0.20000  -0.20000  -0.20000  -0.20000  -0.20000  -0.20000  -0.20000  -0.20000
  -0.10000  -0.10000  -0.10000  -0.10000  -0.10000  -0.10000  -0.10000  -0.10000  -0.10000  -0.10000
   0.00000   0.00000   0.00000   0.00000   0.00000   0.00000   0.00000   0.00000   0.00000   0.00000
   0.10000   0.10000   0.10000   0.10000   0.10000   0.10000   0.10000   0.10000   0.10000   0.10000
   0.20000   0.20000   0.20000   0.20000   0.20000   0.20000   0.20000   0.20000   0.20000   0.20000
   0.30000   0.30000   0.30000   0.30000   0.30000   0.30000   0.30000   0.30000   0.30000   0.30000
   0.40000   0.40000   0.40000   0.40000   0.40000   0.40000   0.40000   0.40000   0.40000   0.40000

x =

  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000
  -0.50000  -0.40000  -0.30000  -0.20000  -0.10000   0.00000   0.10000   0.20000   0.30000   0.40000

theta =

  -2.35619  -2.24554  -2.11122  -1.95130  -1.76819  -1.57080  -1.37340  -1.19029  -1.03038  -0.89606
  -2.46685  -2.35619  -2.21430  -2.03444  -1.81577  -1.57080  -1.32582  -1.10715  -0.92730  -0.78540
  -2.60117  -2.49809  -2.35619  -2.15880  -1.89255  -1.57080  -1.24905  -0.98279  -0.78540  -0.64350
  -2.76109  -2.67795  -2.55359  -2.35619  -2.03444  -1.57080  -1.10715  -0.78540  -0.58800  -0.46365
  -2.94420  -2.89661  -2.81984  -2.67795  -2.35619  -1.57080  -0.78540  -0.46365  -0.32175  -0.24498
   3.14159   3.14159   3.14159   3.14159   3.14159   0.00000   0.00000   0.00000   0.00000   0.00000
   2.94420   2.89661   2.81984   2.67795   2.35619   1.57080   0.78540   0.46365   0.32175   0.24498
   2.76109   2.67795   2.55359   2.35619   2.03444   1.57080   1.10715   0.78540   0.58800   0.46365
   2.60117   2.49809   2.35619   2.15880   1.89255   1.57080   1.24905   0.98279   0.78540   0.64350
   2.46685   2.35619   2.21430   2.03444   1.81577   1.57080   1.32582   1.10715   0.92730   0.78540

那是什么？我认为theta的第一个细胞应该是~0.785398。其他细胞似乎也错了。我错过了什么吗？

Answer 1

自己找到答案。 atan2不仅仅是atan单元格应用。操作数的标志也很重要。

有关详细信息，请参阅：http://sunsite.univie.ac.at/textbooks/octave/octave_17.html

然后关于如何自己实施atan2（正如我正在做的那样）请参阅：http://en.wikipedia.org/wiki/Atan2

Answer 2

Atan2并没有安静，因为它考虑了象限。

请参阅：http://en.wikipedia.org/wiki/Atan2

您的第一个案例是atan(x/y) - Pi

Octave's atan2的奇怪行为

2 个答案: