Add clearer documentation on the format of boxes

[finnergizer]

Love the blog post, documentation, and utility of this!

Was setting it up myself, and had trouble getting results that I thought would be in the boxes when I set up the first inner list to be the bottom left coordinate and the second inner list to be the top right coordinate for the bounding box.

Maybe I am misinterpreting but when I examined the in_box method it appears as if the comparison is done using the first inner list as the bottom right, and the second as the top left.

I could be a bit misguided, so let me know if I was simply utilizing the BOXES incorrectly.

[jonpolak]

is it really bottom right and top left in that order?
it seemed to work bottom left and top right?

[finnergizer]

Here is my initial understanding...

Suppose we have a box with the following two points:

bottom-right: 40, -115 —> box[0][0] = 40, box[0][1] = -115
top-left: 45, -120 —> box[1][0] = 45, box[1][1] = -120

a valid point in this box is 42, -118
coords[0]=42
coords[1]=-118

Let’s sub this into the conditional statement in in_box

if box[0][0] < coords[0] < box[1][0] and box[1][1] < coords[1] < box[0][1]:

>>> 40 < 42 < 45 and -120 < -118 < -115
True

This statement evaluates to true with those co-ordinates specifying the box… So in-box returns True as it should.

Conversely if we were to use bottom-left, top-right, the same box would look like:

bottom-left: 40, -120 —> box[0][0] = 40, box[0][1] = -120
top-right: 45, -115 —> box[1][0] = 45, box[1][1] = -115

Again, subbing this into the conditional:

if box[0][0] < coords[0] < box[1][0] and box[1][1] < coords[1] < box[0][1]:

We get:

>>> 40 < 42 < 45 and -115 <  -118 < -120
False

Which is false by the second part of the conditional…

So in-box returns False when it should return true if the box was defined by bottom-left, top-right.