Thank you, Hermann. Your game is very clever!!
> On Nov 15, 2015, at 12:49 AM, [-hh] wrote:
>
>> Roger G. wrote:
>> Jim, I'm just now trying to catch up on this discussion and I see that no
>> one has answered your question. I can’t answer either and wonder what’s
>> going on???
>> BTW, I bel
ity of the
> method for calculating the area of a polygon.
>
> You’re probably right about the minus sign.
>
> Jim
>
>>
>> Message: 23
>> Date: Sat, 14 Nov 2015 18:37:13 -0800
>> From: Roger Guay
>> To: How to use LiveCode
>> Subject: R
> Roger G. wrote:
> Jim, I'm just now trying to catch up on this discussion and I see that no one
> has answered your question. I can’t answer either and wonder what’s going
> on???
> BTW, I believe you should have a negative sign in front of the square bracket
> . . . not that that helps at all
>
> Message: 23
> Date: Sat, 14 Nov 2015 18:37:13 -0800
> From: Roger Guay
> To: How to use LiveCode
> Subject: Re: Area of Irregular Polygon
> Message-ID: <868cedf8-5e56-46dc-b88c-bb6a68cd4...@mac.com>
> Content-Type: text/plain; charset=utf-8
>
> Jim,
>
Jim,
I'm just now trying to catch up on this discussion and I see that no one has
answered your question. I can’t answer either and wonder what’s going on???
BTW, I believe you should have a negative sign in front of the square bracket .
. . not that that helps at all!
Cheers,
Roger
> On
for those on the list like me who can only iteratively add 1 to a variable
and that have 10 seconds to spare to get at the area of a polygon:
here is what the screen thinks it is:
---
on mouseUp
put "poly" into pName
if not (there is a graphic
> James H. wrote:
> Multiplying this out you get:
>
> x(i)*y(i+1) - x(i+1)y(i) + [x(i+1)* y(i+1) - x(i)* y(i)]
>
> So THE SAME EXPRESSION as in the centroid method EXCEPT for the added term in
> square brackets. So, WHY THE DIFFERENCE?
>
> In calculating this sum all of the intermediate t
Very interesting discussion.
However, I was puzzled by the following term in the sum used to calculate the
area of a polygon--labeled the centroid method.
x(i)*y(i+1) - x(i+1)y(i)
Where does this come from? If one were using the traditional method of
calculating the area under a curve (per
> Alex T. wrote:
> For the area calculation, it is actually marginally faster without the
> "delete line 1 of p" - i.e. as Geoff Canyon suggested.
> ...
> So omitting the "delete line 1 of p" is more efficient - as well as
> being one line fewer of code.
You are right, of course. I read the thre
r of code.
Geoff C strikes again !
-- Alex.
On 10/11/2015 21:37, [-hh] wrote:
In the thread ("Area of irregular Polygon") I've seen a very fast technique.
I tested this technique and found it extremely fast.
Thus I would like to summarize and contribute also the centroid formulas,
In the thread ("Area of irregular Polygon") I've seen a very fast technique.
I tested this technique and found it extremely fast.
Thus I would like to summarize and contribute also the centroid formulas, for
our collections.
Look at non-selfintersecting (simple) polygons.
The cen
Hi Peter,
No, it doesn't assume convexity - what it does assume is
non-self-overlapping, (loosely aka non-self-intersecting).
A simple but non-convex shape, like (excuse the lack of line-drawing in
email :-)
B C
D
A E
For simplicity, pretend the shape is all in th
On 08/11/2015 00:43, Alex Tweedly wrote:
Actually, you should shorten the maths - makes it a bit more efficient
function getArea pPts
if line 1 of pPts <> line -1 of pPts then return 0
put 0 into tArea
put empty into oldL
repeat for each line L in pPts
if oldL is not empt
Thank you. I just might work on this….
> On Nov 8, 2015, at 3:38 AM, [-hh] wrote:
>
>> Roger Guay wrote:
>> Can anyone think of an easy way of getting the area of an Irregular polygon?
>
> This goes nearly one-to-one into LC scripts:
> https://en.wikipedia.org/wiki/Polygon#Area_and_centroid
>
> Roger Guay wrote:
> Can anyone think of an easy way of getting the area of an Irregular polygon?
This goes nearly one-to-one into LC scripts:
https://en.wikipedia.org/wiki/Polygon#Area_and_centroid
There are also considerations for self-intersecting polygons.
=
I donated to Wikipedia.
Important to note that this method of calculating the area of a polygon
will fail if the polygon crosses itself. As long as the polygon is simple,
it works.
On Sat, Nov 7, 2015 at 8:30 PM, Roger Guay wrote:
> This is great . . . Thanks, guys!!!
>
>
> > On Nov 7, 2015, at 4:56 PM, Geoff Canyon w
You could speed it up a bit more and simplify a bit like so:
put line 1 of pPts into oldL
repeat for each line L in line 2 to -1 of pPts
add (item 1 of L - item 1 of oldL) * ( item 2 of oldL + item 2 of
L) / 2 to tArea
put L into oldL
end repeat
On Sat, Nov 7,
Beautiful, Alex. I was working on this idea myself, but your scripts is so much
more elegant!
Thanks,
Roger
> On Nov 7, 2015, at 4:43 PM, Alex Tweedly wrote:
>
> Actually, you should shorten the maths - makes it a bit more efficient
>
>
> function getArea pPts
> if line 1 of pPts <> lin
Actually, you should shorten the maths - makes it a bit more efficient
function getArea pPts
if line 1 of pPts <> line -1 of pPts then return 0
put 0 into tArea
put empty into oldL
repeat for each line L in pPts
if oldL is not empty then
-- put item 1 of L - it
Roger,
try this (I've done some minimal testing, so do please check it ...)
it assumes the polygon is closed
function getArea pPts
if line 1 of pPts <> line -1 of pPts then return 0
put 0 into tArea
put empty into oldL
repeat for each line L in pPts
if oldL is not empty then
Thanks very much, Scott. I do have a long points list that I would have to
manipulate even before apply this technique. I’m not looking forward to that,
but I may have to go this route.
Cheers,
Roger
> On Nov 7, 2015, at 12:05 PM, Scott Rossi wrote:
>
> It looks like this could translate to
It looks like this could translate to LC if you have the point locations
of your polygon:
https://www.mathsisfun.com/geometry/area-irregular-polygons.html
Regards,
Scott Rossi
Creative Director
Tactile Media, UX/UI Design
On 11/7/15, 2:01 PM, "use-livecode on behalf of Roger Guay"
wrote:
Can anyone think of an easy way of getting the area of an Irregular polygon?
Thanks,
Roger
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