我正在学习模糊系统课程,用电脑记录我的笔记。这意味着我不时需要在电脑上绘制图形。由于这些图形非常明确,我认为使用
numpy
绘制它们是个好主意(我用LaTeX做笔记,对Python shell也很熟悉,所以我想我能应付得来)。
模糊隶属函数的图形通常是高度分段的,例如:
numpy.piecewise
的以下代码(但是出现了一个晦涩的错误):In [295]: a = np.arange(0,5,1)
In [296]: condlist = [[b<=a<b+0.25, b+0.25<=a<b+0.75, b+0.75<=a<b+1] for b in range(3)]
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-296-a951e2682357> in <module>()
----> 1 condlist = [[b<=a<b+0.25, b+0.25<=a<b+0.75, b+0.75<=a<b+1] for b in range(3)]
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
In [297]: funclist = list(itertools.chain([lambda x:-4*x+1, lambda x: 0, lambda x:4*x+1]*3))
In [298]: np.piecewise(a, condlist, funclist)
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-298-41168765ae55> in <module>()
----> 1 np.piecewise(a, condlist, funclist)
/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/numpy/lib/function_base.pyc in piecewise(x, condlist, funclist, *args, **kw)
688 if (n != n2):
689 raise ValueError(
--> 690 "function list and condition list must be the same")
691 zerod = False
692 # This is a hack to work around problems with NumPy's
ValueError: function list and condition list must be the same
目前,我对如何绘制这个函数感到相当困惑。我真的不理解错误消息,这进一步阻碍了我调试的努力。
最终,我希望将此函数绘制并导出为EPS文件,因此我也希望在这方面得到任何帮助。
b <= a < b + 0.25
必须写成(b <= a) & (a < b + 0.25)
。 - Warren Weckesser