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I am trying to construct a matrix object out of an array. The array has a length of 25, and what I'm trying to do is construct a 5x5 matrix out of it. I have used both numpy.asmatrix() and the matrix constructor but both result in a matrix that has a length of 1. So, what's basically happening is all the elements of the array are considered a tuple and inserted into the newly-created matrix. Is there any way around this so I can accomplish what I want?

EDIT: When I wrote "array", I naively meant a vanilla python list and not an actual numpy.array which would make things a lot simpler. A mistake on my part.

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Think you probably just want .reshape():

In [2]: a = np.arange(25) In [3]: a Out[3]: array([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]) In [4]: a.reshape(5,5) Out[4]: array([[ 0, 1, 2, 3, 4], [ 5, 6, 7, 8, 9], [10, 11, 12, 13, 14], [15, 16, 17, 18, 19], [20, 21, 22, 23, 24]])

You can also convert it into an np.matrix after if you need things from that:

In [5]: np.matrix(a.reshape(5,5)) Out[5]: matrix([[ 0, 1, 2, 3, 4], [ 5, 6, 7, 8, 9], [10, 11, 12, 13, 14], [15, 16, 17, 18, 19], [20, 21, 22, 23, 24]])

EDIT: If you've got a list to start, it's still not too bad:

In [16]: l = range(25) In [17]: np.matrix(np.reshape(l, (5,5))) Out[17]: matrix([[ 0, 1, 2, 3, 4], [ 5, 6, 7, 8, 9], [10, 11, 12, 13, 14], [15, 16, 17, 18, 19], [20, 21, 22, 23, 24]])
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I tried reshape() and got the error below which really confuses me: ValueError: total size of new array must be unchanged
That means that for your call to arr.reshape(x, y), x * y is not equal to len(arr).
Nevermind, a mistake on my part. The problem is that I'm trying to create a matrix out of a list (instead of an actual numpy array). I'll edit the post. Your answer is fine. Cheers.
@AutomEng: If his answer is fine, you should accept the answer
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You can simply simulate a Matrix by using a 2-dimensional array with 5 spaces in each direction:

>>>Matrix = [[0 for x in range(5)] for x in range(5)]

And access the elemets via:

>>>Matrix[0][0]=1

To test the output, print it:

>>>Matrix [[1, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]

If you need a specific implementation like numpy, please specify your question.

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row = int(input("Enter the number of Rows: \n")) col = int(input("Enter the number of Column: \n")) print("Enter how many elements you want: \n") num1 = row * col print('Enter your elements in array: ') for i in range(num1): n = int(input("Element " + str(i + 1) + " : ")) num_array1.append(n) arr = np.array([num_array1]) newarr = arr.reshape(row, col) print(newarr) print(type(newarr))

This should help to create matrix type arrays with custom user input

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If you have an array of length 25, you can turn it into a 5x5 array using reshape().

A = np.arange(25) # length 25 B = A.reshape(5, 5) # 5x5 array

You will however have to make sure that the elements in your array end up in the correct place in the newly formed 5x5 array.

Although there is a numpy.matrix class, I would suggest you forget about it and only use numpy.ndarray. The only difference is you have to use np.dot (or @ in case of newer Python/Numpy) for matrix multiplication instead of *. The matrix class have a tendency to introduce mistakes in your code unless you are very careful.

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