[英]MATLAB TO PYTHON conversion [ValueError: operands could not be broadcast together with shapes (120,) (6,) ]
So this is my python code所以这是我的 python 代码
import numpy as np
n = 3
T = 100
ts = .2*(100/(2*n-3))
tv = .6*((100-((2*n-3)*ts))/(2*(n-1)))
m1 = np.arange(0,tv,0.1);
x1 = 0.5*(1-(np.cos(np.pi*(m1/tv))))
xa = x1;
#%travelling from right to left
xd = np.flip(xa)
xw = []
for i in range(1,n-1):
if i==1:
pass
else:
xd = xd-1
#%standing at one point
for f in np.arange(1,ts):
mini = np.amin(xd)
xw.append(mini)
if i==1:
xm=np.array([xd,xw])
else:
xm = np.array([xm,xd,xw])
xm = abs(np.amin(xm)) + xm
When I run it there comes up a big pile of error block.当我运行它时,会出现一大堆错误块。 I know that arrays must have the same rank to perform mathematical operations but I don't know how to do that here.
我知道 arrays 必须具有相同的等级才能执行数学运算,但我不知道如何在此处执行此操作。
This is error block that comes up when I run the code这是我运行代码时出现的错误块
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-7-64722470b31e> in <module>
32 xm = np.array([xm,xd,xw])
33
---> 34 xm = abs(np.amin(xm)) + xm
35
36
<__array_function__ internals> in amin(*args, **kwargs)
~\anaconda3\lib\site-packages\numpy\core\fromnumeric.py in amin(a, axis, out, keepdims, initial, where)
2856 6
2857 """
-> 2858 return _wrapreduction(a, np.minimum, 'min', axis, None, out,
2859 keepdims=keepdims, initial=initial, where=where)
2860
~\anaconda3\lib\site-packages\numpy\core\fromnumeric.py in _wrapreduction(obj, ufunc, method, axis, dtype, out, **kwargs)
85 return reduction(axis=axis, out=out, **passkwargs)
86
---> 87 return ufunc.reduce(obj, axis, dtype, out, **passkwargs)
88
89
ValueError: operands could not be broadcast together with shapes (120,) (6,)
Heres the Matlab code这是 Matlab 代码
xd = flip(xa);
for i= 1:n-1
if i==1
else
xd = xd-1;
end%standing at one point
for f = 1:ts
xw(f) = min(xd);
end
if i==1
xm=[xd,xw];
else
xm = [xm,xd,xw];
end
end
xm = abs(min(xm))+xm;
disp(xm);
And this is the output I get from running the MATLAB code which is also the output I'm expecting from my python code.这是我从运行 MATLAB 代码得到的 output,这也是我期望从我的 python 代码得到的 output。
>>
Columns 1 through 13
2.0000 1.9998 1.9993 1.9985 1.9973 1.9957 1.9938 1.9916 1.9891 1.9862 1.9830 1.9794 1.9755
Columns 14 through 26
1.9713 1.9668 1.9619 1.9568 1.9513 1.9455 1.9394 1.9330 1.9263 1.9193 1.9121 1.9045 1.8967
Columns 27 through 39
1.8886 1.8802 1.8716 1.8627 1.8536 1.8442 1.8346 1.8247 1.8147 1.8044 1.7939 1.7832 1.7723
Columns 40 through 52
1.7612 1.7500 1.7386 1.7270 1.7153 1.7034 1.6913 1.6792 1.6669 1.6545 1.6420 1.6294 1.6167
Columns 53 through 65
1.6040 1.5911 1.5782 1.5653 1.5523 1.5392 1.5262 1.5131 1.5000 1.4869 1.4738 1.4608 1.4477
Columns 66 through 78
1.4347 1.4218 1.4089 1.3960 1.3833 1.3706 1.3580 1.3455 1.3331 1.3208 1.3087 1.2966 1.2847
Columns 79 through 91
1.2730 1.2614 1.2500 1.2388 1.2277 1.2168 1.2061 1.1956 1.1853 1.1753 1.1654 1.1558 1.1464
Columns 92 through 104
1.1373 1.1284 1.1198 1.1114 1.1033 1.0955 1.0879 1.0807 1.0737 1.0670 1.0606 1.0545 1.0487
Columns 105 through 117
1.0432 1.0381 1.0332 1.0287 1.0245 1.0206 1.0170 1.0138 1.0109 1.0084 1.0062 1.0043 1.0027
Columns 118 through 130
1.0015 1.0007 1.0002 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.9998 0.9993
Columns 131 through 143
0.9985 0.9973 0.9957 0.9938 0.9916 0.9891 0.9862 0.9830 0.9794 0.9755 0.9713 0.9668 0.9619
Columns 144 through 156
0.9568 0.9513 0.9455 0.9394 0.9330 0.9263 0.9193 0.9121 0.9045 0.8967 0.8886 0.8802 0.8716
Columns 157 through 169
0.8627 0.8536 0.8442 0.8346 0.8247 0.8147 0.8044 0.7939 0.7832 0.7723 0.7612 0.7500 0.7386
Columns 170 through 182
0.7270 0.7153 0.7034 0.6913 0.6792 0.6669 0.6545 0.6420 0.6294 0.6167 0.6040 0.5911 0.5782
Columns 183 through 195
0.5653 0.5523 0.5392 0.5262 0.5131 0.5000 0.4869 0.4738 0.4608 0.4477 0.4347 0.4218 0.4089
Columns 196 through 208
0.3960 0.3833 0.3706 0.3580 0.3455 0.3331 0.3208 0.3087 0.2966 0.2847 0.2730 0.2614 0.2500
Columns 209 through 221
0.2388 0.2277 0.2168 0.2061 0.1956 0.1853 0.1753 0.1654 0.1558 0.1464 0.1373 0.1284 0.1198
Columns 222 through 234
0.1114 0.1033 0.0955 0.0879 0.0807 0.0737 0.0670 0.0606 0.0545 0.0487 0.0432 0.0381 0.0332
Columns 235 through 247
0.0287 0.0245 0.0206 0.0170 0.0138 0.0109 0.0084 0.0062 0.0043 0.0027 0.0015 0.0007 0.0002
Columns 248 through 254
0 0 0 0 0 0 0
>>
When you ran this code, did you git the ragged array
warning?当你运行这段代码时,你有没有 git 参差不齐的
ragged array
警告? If so, why did you ignore it?如果是这样,你为什么忽略它? Or are you running such old
numpy
that it didn't give the warning?还是您正在运行这么旧的
numpy
以致于它没有发出警告?
<ipython-input-1-7dab9a6384c7>:24: VisibleDeprecationWarning: Creating an ndarray from ragged nested sequences (which is a list-or-tuple of lists-or-tuples-or ndarrays with different lengths or shapes) is deprecated. If you meant to do this, you must specify 'dtype=object' when creating the ndarray.
xm=np.array([xd,xw])
In [2]: xm
Out[2]:
array([array([9.99828662e-01, 9.99314767e-01, 9.98458667e-01, 9.97260948e-01,
9.95722431e-01, 9.93844170e-01, 9.91627454e-01, 9.89073800e-01,
...
1.54133313e-03, 6.85232623e-04, 1.71337512e-04, 0.00000000e+00]),
list([0.0, 0.0, 0.0, 0.0, 0.0, 0.0])], dtype=object)
In [3]: xm.shape
Out[3]: (2,)
In [4]: xm.dtype
Out[4]: dtype('O')
In [5]: xm[0].shape
Out[5]: (120,)
In [7]: len(xm[1])
Out[7]: 6
xm
is object dtype containing one array and one list. xm
是 object dtype,包含一个数组和一个列表。 Their lengths match the ones stated in the error: shapes (120,) (6,)
它们的长度与错误中所述的长度相匹配:
shapes (120,) (6,)
You can't do np.min
on such an array.您不能在这样的数组上执行
np.min
。
I won't try to sort out the logic of your xm
constructor, but I see that you use xw
as list and list append, but xm
as array and np.array([...])
to make new values in the loop.我不会尝试理清你的
xm
构造函数的逻辑,但我看到你使用xw
作为列表和列表 append,但xm
作为数组和np.array([...])
在循环中生成新值. Repeated np.array
in a loop is not a good idea;在循环中重复
np.array
不是一个好主意; it is slow and prone to errors.它很慢并且容易出错。 The same applies to use
np.concatenate
(or one its derivatives) in a loop.这同样适用于在循环中使用
np.concatenate
(或其衍生物之一)。 If you are going to work iteratively, stick with lists, and make the arrays, if needed, with one call at the end.如果您要反复工作,请坚持使用列表,并在需要时拨打 arrays,最后打一个电话。
Back when I worked with MATLAB, around version 3.9, we tried to avoid loops because they were slow.当我使用 MATLAB 时,大约是 3.9 版,我们试图避免循环,因为它们很慢。 Since then MATLAB has add
jit
compilation so there isn't much of a time penalty.从那时起 MATLAB 添加
jit
编译,因此没有太多时间损失。 In numpy
it is still best to avoid loops, or to use numba
to compile them. numpy
还是最好避免循环,或者用numba
来编译。
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