How to find matches in numpy arrays automatically in a for loop in python

Question

I wat to search for indices of an array in two other arrays and want to find out where they match. Firstly, I have a variable which says how many points will be matched It is called brk. This brk equals the length of my search array (searched). In my simple case brk = 2 which means I will have 4 match points (brk * 2). So, I must split my search arry into brk halves and then search each half in each main array (main_x_arr and main_y_arr). I have always one search array and two main arrays, but brk changes and says ho to search for indices. At the moment I am creating each match manually but I am trying to create matches auromatically. This is my code:

searched=np.array([[1., 2.], [-3., 1.]])
brk=len(searched)
main_y_arr=np.array([[1., 5.], [8., 3.], [-3., 8.], [2., 4.]])
main_x_arr=np.array([[1., 7.], [-3., 1.], [4., 7.], [2., 4.]])
match1= np.min (np.unique (np.where((main_y_arr==searched[:int (len(searched)/2)].reshape (-1,1)[:,None]).any(-1))[1]))
match2= np.max (np.unique (np.where((main_x_arr==searched[:int (len(searched)/2):].reshape (-1,1)[:,None]).any(-1))[1]))
match3= np.min (np.unique (np.where((main_y_arr==searched[int (len(searched)/2):].reshape (-1,1)[:,None]).any(-1))[1]))
match4= np.max (np.unique (np.where((main_x_arr==searched[int (len(searched)/2):].reshape (-1,1)[:,None]).any(-1))[1]))

As it can be seen, I am creating each match but I want to find a way to firstly kno I will have 2 * brk matches. Then, split searched array into the number of brk and after that search for each split in each array which makes 4 matches. If the length of my searched array equals 3, then I will have thre splits and finall 6 (eactly like repeating match1 and match2 for three slices to make 6 matches). Or if it is 1, I will have only 2 matches (exactly like having match1 and match2 for only one single slide) because it cannot be splitted anymore. In advance I do appreciate any help and feedback.

can you describe what you are trying to accomplish in a sentence ? I'm mostly guessing here: (something like) I have a list of (x,y)-points [seached] i want to search for in a list of points [main] ... — lwohlhart
– lwohlhart, Commented Mar 11, 2021 at 10:08
Dear @lwohlhart, Thanks for devoting time to me. in a sentence: finding the indices of searched in my main arrays. But the point is that it is not always simple. Sometimes I need to split searched rray and look for each split separately and find the mathed index. — Link_tester
– Link_tester, Commented Mar 11, 2021 at 10:11
okay, do i understand it correctly that main_x_arr and main_y_arr together define the x and y coordinates of your main-points? So there's are the points [(1,1), (7,5), (-3,8),(1,3), .......] ? If so then I think your life would be easier if you reorganize the declaration of your main points array ( even if it's just for the search ) — lwohlhart
– lwohlhart, Commented Mar 11, 2021 at 10:16
@lwohlhart, unfortunately they are not x and y coordinates of the points. They are just some numbers. In fact, they are numbers of some points in x and y directions and I want to find the matches between these numbers and numbers stored in searched array. — Link_tester
– Link_tester, Commented Mar 11, 2021 at 10:21
okay i think we're coming close: the actual question at hand is : can you formulate what makes a match ( mathematically or in words ) — lwohlhart
– lwohlhart, Commented Mar 11, 2021 at 10:23

lwohlhart · Accepted Answer · 2021-03-11 11:06:36Z

1

after a lengthy discussion we decided that this solves the OPs requirements:

matches = []
for current_search in searched:
    current_search_reshaped = current_search.reshape(-1,1,1)
    match_min = np.min(np.unique(np.where((main_y_arr == current_search_reshaped).any(-1))[1]))
    match_max = np.max(np.unique(np.where((main_x_arr == current_search_reshaped).any(-1))[1]))
    matches.append((match_min, match_max))

answered Mar 11, 2021 at 11:06

lwohlhart

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