Question

我是Theano的初学者，但尽管进行了大量研究，我仍然不明白为什么以下代码

from matplotlib.pyplot import plot
from numpy import linspace
import theano.tensors as T
A = linspace(0,1,100)
plot(A, T.sqrt(A))

返回此错误消息

ValueError                                Traceback (most recent call last)
<ipython-input-21-48fbaf974de7> in <module>()
----> 1 plot(L1, L1+Lx)

C:\Python27\lib\site-packages\matplotlib\pyplot.pyc in plot(*args, **kwargs)
   2985         ax.hold(hold)
   2986     try:
-> 2987         ret = ax.plot(*args, **kwargs)
   2988         draw_if_interactive()
   2989     finally:

C:\Python27\lib\site-packages\matplotlib\axes.pyc in plot(self, *args, **kwargs)
   4135         lines = []
   4136 
-> 4137         for line in self._get_lines(*args, **kwargs):
   4138             self.add_line(line)
   4139             lines.append(line)

C:\Python27\lib\site-packages\matplotlib\axes.pyc in _grab_next_args(self, *args, **kwargs)
    315                 return
    316             if len(remaining) <= 3:
--> 317                 for seg in self._plot_args(remaining, kwargs):
    318                     yield seg
    319                 return

C:\Python27\lib\site-packages\matplotlib\axes.pyc in _plot_args(self, tup, kwargs)
    293             x = np.arange(y.shape[0], dtype=float)
    294 
--> 295         x, y = self._xy_from_xy(x, y)
    296 
    297         if self.command == 'plot':

C:\Python27\lib\site-packages\matplotlib\axes.pyc in _xy_from_xy(self, x, y)
    212         if self.axes.xaxis is not None and self.axes.yaxis is not None:
    213             bx = self.axes.xaxis.update_units(x)
--> 214             by = self.axes.yaxis.update_units(y)
    215 
    216             if self.command != 'plot':

C:\Python27\lib\site-packages\matplotlib\axis.pyc in update_units(self, data)
   1334         """
   1335 
-> 1336         converter = munits.registry.get_converter(data)
   1337         if converter is None:
   1338             return False

C:\Python27\lib\site-packages\matplotlib\units.pyc in get_converter(self, x)
    146             except AttributeError:
    147                 # not a masked_array
--> 148                 converter = self.get_converter(xravel[0])
    149                 return converter
    150 

C:\Python27\lib\site-packages\matplotlib\units.pyc in get_converter(self, x)
    150 
    151         if converter is None and iterable(x):
--> 152             for thisx in x:
    153                 # Make sure that recursing might actually lead to a solution,
    154                 # if we are just going to re-examine another item of the same

C:\Python27\lib\site-packages\theano\tensor\var.pyc in __iter__(self)
    416     def __iter__(self):
    417         try:
--> 418             for i in xrange(theano.tensor.basic.get_vector_length(self)):
    419                 yield self[i]
    420         except TypeError:

C:\Python27\lib\site-packages\theano\tensor\basic.pyc in get_vector_length(v)
   3732     if v.owner and isinstance(v.owner.op, Shape):
   3733         return v.owner.inputs[0].type.ndim
-> 3734     raise ValueError("length not known")
   3735 
   3736 

ValueError: length not known

当我在控制台中键入T.sqrt（A）时，它返回“Elemwise {sqrt，no_inplace} .0”，我无法得到T.sqrt（A）的值。我想知道我是否可以将matplotlib与theano张量一起使用，否则如何将aano函数映射到ndarray类型的numpy数组列表。

Answer 1

你得到“Elemwise {sqrt，no_inplace} .0”的原因是因为Theano是象征性的，所以张量在评估之前没有值。解决这个问题：

from matplotlib.pyplot import plot
from numpy import linspace
import theano.tensor as T
A = linspace(0,1,100)
plot(A, T.sqrt(A).eval())

评估张量并获得其数值。

此外，您应该导入theano.tensor，而不是theano.tensors。

ValueError：在Theano中映射列表时未知长度

1 个答案: