Shoelace formula for polygonal area: Difference between revisions
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# Even simpler: |
# Even simpler: |
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# In python we can take an advantage of that x[-1] refers to the last element in an array, same as x[N-1]. |
# In python we can take an advantage of that x[-1] refers to the last element in an array, same as x[N-1]. |
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# Introducing the index i=[0,1,2,...,N-1]; i-1=[-1,0,...,N- |
# Introducing the index i=[0,1,2,...,N-1]; i-1=[-1,0,...,N-2]; N is the number of vertices of a polygon. |
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# Thus x[i] is a sequence of the x-coordinate of the polygon vertices, x[i-1] is the sequence shifted by 1 index. |
# Thus x[i] is a sequence of the x-coordinate of the polygon vertices, x[i-1] is the sequence shifted by 1 index. |
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# Note that the shift must be negative. The positive shift x[i+1] results in an error: x[N] index out of bound. |
# Note that the shift must be negative. The positive shift x[i+1] results in an error: x[N] index out of bound. |
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