Is there a way to sort a set of co-ordinates in a top-to-bottom, left-to-right precedence as they appear?

Question

I have a list of XY co-ordinates, and I am looking for a way to sort them as they appear on the plot with top-to-bottom, left-to-right precedence.

I tried sorting them as a tuple in Python but it didn't work.

Here are the (normalized) co-ordinates:

(0.48425699105850684, 0.4852200502470339) (0.8003207976544613, 0.1794844315136523) (0.663158173206857, 0.19739922702645016) (0.26770425263394393, 0.20288883507443173) (0.5214529814719886, 0.2032096846467844) (0.4768268032594222, 0.3875097802042241) (0.5400594055964151, 0.5870619715600098) (0.5445470099105095, 0.8064964338255158)

Keep in mind that this is basically just vertical sort for floats — Mad Physicist, Jun 21 '22 at 02:28

MBo · Answer 1 · 2022-06-21T02:24:39.817

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So you need to use Y-coordinate as primary key, X-coordinate as secondary key.
One of possible ways in Python:

lst.sort(key = lambda x: (x[1], x[0]))

if your Y-axis direction is down (otherwise -x[1])

Example:

lst = [(3, 8), (5, 3), (1, 5), (2, 3), (7, 4), (4, 5)]
lst.sort(key = lambda x: (x[1], x[0]))
print(lst)

>>[(2, 3), (5, 3), (7, 4), (1, 5), (4, 5), (3, 8)]

edited Jun 21 '22 at 02:24

answered Jun 20 '22 at 18:14

MBo

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Maybe `x[::-1]`? – Olvin Roght Jun 20 '22 at 18:18
@Olvin Roght There is a lot of approaches. I am not sure how coordinate axes are oriented, so left the opportunity to inverse one of them – MBo Jun 20 '22 at 18:22
Hey I tried this but it did not work, thanks for the response! – fortyTwo102 Jun 20 '22 at 21:05
@fortyTwo102 But I tried and it does work. provides order like strings in text . See example – MBo Jun 21 '22 at 02:24

score 0 · Answer 2 · answered Jun 20 '22 at 21:06

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I eventually ended up using the product of the X and Y coordinates as the sorting key. It worked for my test cases!

answered Jun 20 '22 at 21:06

fortyTwo102

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This approach gives rather exotic point ordering. – MBo Jun 21 '22 at 02:27

Is there a way to sort a set of co-ordinates in a top-to-bottom, left-to-right precedence as they appear?

2 Answers2