从随机2D numpy数组中提取ith和ith + 1

Question

I have a numpy array consisting of

[1,3,8,6,0,2,4,5,9,7]

This array is a random array consisting of 10 numbers 0-9.

I also have a 2D numpy array, a 10X10 2D numpy array with numerical values.

I would like to use my 1D numpy array (above) to access specific instances in my 2D numpy array, by looping through the 1D array

1. Loop 1: takes in 1 and 3, and finds the value at [1:3] in my 2D numpy array.
2. Loop 2: takes in 3 and 8, and finds the value at [3:8] in my 2D numpy array.

.

10. Loop 10: takes in 7 and 1, and finds the value at [7:1] in my 2D numpy array.

I would like to add up these values in my 2D numpy array.

so far I have : array=[1,3,8,6,0,2,4,5,9,7]

values =0
for i in range (0, len(array)): #this is 10
    a=array2[i,array[i]+1]  #array2 is the 2D numpy array with the values
    values=values+a

This works to some degree but how to I get it to access the last element to the first? ie find [7,1]

Answer 1

You can do the slicing twice to make it work.

values = 0
for i in range(len(array)): 
    a = Matrix[array[i],array[i+1]]
    values += a

Also, the array you put has 11 elements which means the 10-th loop will not be what you intended.

Answer 2

You can use simple slicing to make this work.

arr = np.random.randint(0, 10, (10,10))
pos = np.array([1,3,8,6,0,2,4,5,9,7])
pos = np.append(pos, pos[0])

rows = pos[0:-1]
cols = pos[1:]

result = sum(arr[rows, cols])

Answer 3

I'm not sure I fully understood what you were trying to achieve but... What about something like this?

a = np.array([1,3,8,6,0,9,2,4,5,9,7])
b = np.array(range(100)).reshape(10,10)

for i in range (len(a)):
    print (a[i%len(a)],a[(i+1)%len(a)])
    print (b[a[i%len(a)],a[(i+1)%len(a)]])

I removed 10 from the a array to avoid an index out of range error.

I also took the value [x,y] (and not the range [x:y] from the 2D array.