1
I need to calculate the transposed matrix using the python map function. But, I’m not able to solve.
def transp(a):
for i in range(2):
for j in a:
return [a[i][j]]
list (map(transp,matrix))
The following error message appears - Typeerror: 'int' Object is not subscriptable
what I do to fix this bug?
4
A solution
a = [[1, 2, 3, 4], [4, 6, 7, 9], [4, 3, 2, 1]]
*b, = zip(*a)
print(b)
Exit
[(1, 4, 4), (2, 6, 3), (3, 7, 2), (4, 9, 1)]
4
A solution using list comprehension:
A=[[1,2],[4,6]]
#printa as linhas da matriz A
for i in A:
print(i)
A_t=[[k[0] for k in A],[k[1] for k in A]]
#printa as linhas da transposta de A
for i in A_t:
print(i)
This solution uses the fact that an array can be seen as a list of lists and that transposition simply consists of transforming rows into columns.
Operations with arrays can become very complex depending on the application. For this reason I recommend studying implementations of this and other matrix operations in numpy and/or sympy modules.
4
Source matrix
M =[[1,2],[3,4],[5,6]]
Printing
for j in M:
print(j)
Exit
[1, 2]
[3, 4]
[5, 6]
Transposed
Creating the matrix
M_t = list(map(list, zip(*M)))
Printing
for j in M_t:
print(j)
Exit
[1, 3, 5]
[2, 4, 6]
Using numpy
import numpy as np
M =[[1,2],[3,4],[5,6]]
M_t = np.array(M).T
Beautiful solution to see! What clean code!
Thanks @Matthew, big hug!
4
First, for you to calculate the transposed of an "A" matrix, you need the "A" matrix. Another thing, for you to calculate the transpose of a matrix with the help of the function map(), you will need to implement an anonymous function (lambda). In this case, the code can be implemented as follows:
a = [[1, 2], [4, 6]]
transposta = list(map(lambda *i: [j for j in i], *a))
print(transposta)
Note that for this code I used the matrix:
a = [[1, 2], [4, 6]]
When executing this code, we receive as a result:
[[1, 4], [2, 6]]
Just to reinforce what has already been said in the other answer, matrices is a very long subject and we can have better results if we study libraries better numpy and scipy.
If you want to implement a def function to calculate the transpose of the matrix you can implement the following code:
def transposta(m):
return list(map(lambda *i: [j for j in i], *m))
matriz = [[1, 2], [4, 6]]
print(transposta(matriz))
The matrix was in the code, I just didn’t put this bit here, with respect to lambda function, I can only solve this problem with it? There’s no way to use def?
@Wesley Barros, at the level of Python code, there are several ways to calculate the transpose of a matrix. You can implement a function def to calculate the transpose of a matrix.
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