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Have an array of point which are plotted as below . There are column structures in the set of point. enter image description here

How can these points be grouped into different columns?

np.array([[151,  26],[ 30,  26],[511,  27],[747,  30],[609,  28],[930,  30],
   [ 30,  52],[211,  53],[513,  54],[608,  54],[824,  56],[946,  55],
   [106,  87],[187,  87],[512,  89],[609,  90],[725,  90],[823,  92],
   [931,  92],[ 28, 113],[301, 113],[512, 115],[609, 116],[ 28, 142],
   [107, 141],[220, 142],[511, 143],[724, 145],[823, 146],[937, 146],
   [ 29, 168],[308, 168],[512, 171],[ 28, 197],[107, 197],[205, 198],
   [511, 199],[724, 200],[940, 201],[ 29, 222],[307, 223],[217, 244],
   [107, 273],[ 28, 274],[201, 273],[511, 276],[725, 277],[937, 279],
   [ 28, 299],[273, 301],[218, 321],[ 28, 351],[107, 350],[201, 351],
   [511, 354],[723, 354],[947, 356],[ 29, 376],[297, 377]])

Expected output is

enter image description here

where the line is representing each group of coordinates which visually forms a column .

Thanks in advance for your time – if I’ve missed out anything, over- or under-emphasized a specific point let me know in the comments.

Nithin Varghese
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3 Answers3

1

To group the columns by points (grouping by x), you can do something like this.

xy = np.array([
    [151,  26],[ 30,  26],[511,  27],[747,  30],[609,  28],[930,  30],
    [ 30,  52],[211,  53],[513,  54],[608,  54],[824,  56],[946,  55],
    [106,  87],[187,  87],[512,  89],[609,  90],[725,  90],[823,  92],
    [931,  92],[ 28, 113],[301, 113],[512, 115],[609, 116],[ 28, 142],
    [107, 141],[220, 142],[511, 143],[724, 145],[823, 146],[937, 146],
    [ 29, 168],[308, 168],[512, 171],[ 28, 197],[107, 197],[205, 198],
    [511, 199],[724, 200],[940, 201],[ 29, 222],[307, 223],[217, 244],
    [107, 273],[ 28, 274],[201, 273],[511, 276],[725, 277],[937, 279],
    [ 28, 299],[273, 301],[218, 321],[ 28, 351],[107, 350],[201, 351],
    [511, 354],[723, 354],[947, 356],[ 29, 376],[297, 377]])

n = np.unique(xy[:,0])
cols = { i: list(xy[xy[:,0]==i,1]) for i in n }

This creates a dictionary containing column as keys and its corresponding y values. If you want to group by y to get rows then you can simply flip the 0's and 1's and you'll get group by y.

Then, to re-print the graph, you can do this (There is probably a better way of doing this)

x, y = np.array([]), np.array([])
for i in cols.items():
    x = np.append(x, [i[0]] * len(i[1]))
    y = np.append(y, (i[1]))
plt.scatter(x, y) 
plt.show()

Which gives back the original graph.

enter image description here

Taimur
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0

From Scratch

# Create variables
grouped = []
unique = {}

# Get all unique x values and store y as array in dictionary
for point in points:
    unique[point[0]] = unique.get(point[0], []) + point[1]

# Convert the x's into columns of points
for x in unique:
    grouped.append([[x, y] for y in unique[x]])

# Extra polishing
grouped = np.array(grouped)

This creates a new NumPy array:

data = [columns [points within columns]]

Note that this does not handle the re-graphing because not enough information was provided for that section, only the splitting into groups.

Larry the Llama
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0

You can use a defaultdict to append to a list for each point you find in a column.

from collections import defaultdict
d = defaultdict(list)

for point in array:
   x, _ = point
   d[x].append(point)
grouped_by_columns = list(d.values())
Kinille
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