-2

When I try to multiply this by a negative integer it just returns an error

power

I use:

A = np.array([[1,2,0], [2,4,-2], [0,-2,3]])

seralouk
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john777
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4 Answers4

3

From the screenshot, I can see this is homework.

So it asks for the matrix inverse. In maths this is written as A^(-1)

import numpy as np

A = np.array([[1,2,0], [2,4,-2], [0,-2,3]])
np.linalg.inv(A)

array([[-2.  ,  1.5 ,  1.  ],
       [ 1.5 , -0.75, -0.5 ],
       [ 1.  , -0.5 ,  0.  ]])
seralouk
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0

In numpy, you can not raise integers by negative integer powers (Read this).

In python, the ** operator returns the value without any error.

In [6]: A = 20                                                                                                                                                                          

In [7]: print(A ** -1)                                                                                                                                                                  
0.05

You can also use pow(),

In [1]: A = 20

In [2]: pow(20, -1)
Out[2]: 0.05
Premkumar chalmeti
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-1

If you're working with matrices, it's a good idea to ensure that they are instances of the numpy.matrix type rather than the more-generic numpy.ndarray.

import numpy as np
M = np.matrix([[ ... ]])

To convert an existing generic array to a matrix you can also pass it into np.asmatrix().

Once you have a matrix instance M, one way to get the inverse is M.I

To avoid the "integers not allowed" problem, ensure that the dtype of your matrix is floating-point, not integer (specify dtype=float in the call to matrix() or asmatrix())

jez
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    On the contrary, if you're working with matrices, you should use `numpy.ndarray` and *not* the `numpy.matrix` type. See https://stackoverflow.com/q/53254738/270986. – Mark Dickinson Nov 23 '19 at 12:26
-1

To Insert power as negative value assume an another variable and name it "pow" and assign that negative value. Now put below in your code.

pow = -3
value = 5**pow
print(value)

Execute the code and you will see result. Hope it helps...

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