How to sum the frist index in numpy array
Question:
How to sum the first index of array with the number of iterations the max number iteration is 2.
I’ve tried use below code, but I still get wrong result for index number 2.
a = np.array([[858,833,123],
[323,542,927],
[938,361,271],
[679,272,451]])
max_iter = 2
for i in range(max_iter):
for j in range(len(a)):
a[j][0] += i
the results from the code above :
[[859 833 123]
[324 542 927]
[939 361 271]
[680 272 451]]
my expected results is:
[859,833,123],
[325,542,927],
[939,361,271],
[681,272,451]
Answers:
You’re almost there! You’re just adding the wrong value.
The key problem is that you are continuously increasing i.
In reality (I think) you want to add 1 on the first row, 2 on the second, 1 on the third and 2 on the fourth.
Remember the row numbers are index from 1. Therefore you can do % 2 so that the first row, #0, gives 0. You can add 1 to that, to give the increment you want, which is 1.
The second row, #1, gives 1; when you add 1, you get 2, which is the correct increment for that row.
The third row, #2, gives 0; when you add 1, you get 1, which is the correct increment for that row, and so on.
a = np.array([[858,833,123],
[323,542,927],
[938,361,271],
[679,272,451]])
max_iter = 2
for row in range(len(a)):
increment = (row % max_iter) +1
a[row][0] += increment
The question is not clear about requirements, i just take a guess that you want to add a number in range (1, max_iterator) to rows in order, for example:
- add 1 to row 1st
- add 2 to row 2nd
- add 1 to row 3rd
- add 2 to row 4th
- and 1 to row 5th
- and so on
If so, you can do it by following:
a = np.array([[858,833,123],
[323,542,927],
[938,361,271],
[679,272,451]])
max_iter = 2
iter = 0
for i in range(len(a)):
a[i][0] = a[i][0] + (iter % max_iter) + 1
iter += 1
print(a)
Output will be as expected:
[859,833,123],
[325,542,927],
[939,361,271],
[681,272,451]
You can repeat 1 and 2 to len(a) size then add them to the first column of arr
max_iter = 2
arr = [(i % max_iter)+1 for i in range(len(a))]
a[:, 0] += arr
$ print(arr)
[1, 2, 1, 2]
$ print(a)
[[859 833 123]
[325 542 927]
[939 361 271]
[681 272 451]]
How to sum the first index of array with the number of iterations the max number iteration is 2.
I’ve tried use below code, but I still get wrong result for index number 2.
a = np.array([[858,833,123],
[323,542,927],
[938,361,271],
[679,272,451]])
max_iter = 2
for i in range(max_iter):
for j in range(len(a)):
a[j][0] += i
the results from the code above :
[[859 833 123]
[324 542 927]
[939 361 271]
[680 272 451]]
my expected results is:
[859,833,123],
[325,542,927],
[939,361,271],
[681,272,451]
You’re almost there! You’re just adding the wrong value.
The key problem is that you are continuously increasing i.
In reality (I think) you want to add 1 on the first row, 2 on the second, 1 on the third and 2 on the fourth.
Remember the row numbers are index from 1. Therefore you can do % 2 so that the first row, #0, gives 0. You can add 1 to that, to give the increment you want, which is 1.
The second row, #1, gives 1; when you add 1, you get 2, which is the correct increment for that row.
The third row, #2, gives 0; when you add 1, you get 1, which is the correct increment for that row, and so on.
a = np.array([[858,833,123],
[323,542,927],
[938,361,271],
[679,272,451]])
max_iter = 2
for row in range(len(a)):
increment = (row % max_iter) +1
a[row][0] += increment
The question is not clear about requirements, i just take a guess that you want to add a number in range (1, max_iterator) to rows in order, for example:
- add 1 to row 1st
- add 2 to row 2nd
- add 1 to row 3rd
- add 2 to row 4th
- and 1 to row 5th
- and so on
If so, you can do it by following:
a = np.array([[858,833,123],
[323,542,927],
[938,361,271],
[679,272,451]])
max_iter = 2
iter = 0
for i in range(len(a)):
a[i][0] = a[i][0] + (iter % max_iter) + 1
iter += 1
print(a)
Output will be as expected:
[859,833,123],
[325,542,927],
[939,361,271],
[681,272,451]
You can repeat 1 and 2 to len(a) size then add them to the first column of arr
max_iter = 2
arr = [(i % max_iter)+1 for i in range(len(a))]
a[:, 0] += arr
$ print(arr)
[1, 2, 1, 2]
$ print(a)
[[859 833 123]
[325 542 927]
[939 361 271]
[681 272 451]]