Re: point projection on polyline

[Juan Pablo Carbajal]

On Fri, Nov 20, 2015 at 11:02 AM, rcharan51 <address@hidden> wrote:
> and sorry(I almost forgot) here's the code on bpaste
>
> https://bpaste.net/show/dc93ef0c7e20
>
> Best Regards,
>
> Raghu Charan A,
>
> B. Tech (Hons) Civil Engineering (class of 2015),
>
> School of Infrastructure,IIT Bhubaneswar, India.
>
> Email: address@hidden, address@hidden
> Mobile No: +91 8860567691, +91 7205733924
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>
> On Fri, Nov 20, 2015 at 11:35 AM, Raghu Charan A <address@hidden> wrote:
>
>> No need to thank it's mutual. Congratulations !!
>> BTW whom do you support in the clasico?
>> On Nov 17, 2015 17:40, "Juan Pablo Carbajal-2 [via Octave]" <
>> address@hidden> wrote:
>>
>>> On Tue, Nov 17, 2015 at 6:44 AM, rcharan51 <[hidden email]
>>> <http:///user/SendEmail.jtp?type=node&node=4673532&i=0>> wrote:
>>>
>>> > Is there any alternative without calling distancePointEdge inside
>>> > projectPointOnPolyline, which I beleive is the main reason for slow
>>> running
>>> > of the function. I could not understand the algorithm but I found a
>>> similar
>>> > function in Scilab. here's the source code for it
>>> > https://searchcode.com/codesearch/view/25401835/
>>> >
>>> >
>>> >
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>>> Hi,
>>> Thanks for sending the demos, but I did not get anything. Sometimes
>>> the mailing list filters attachments. Better post the code in Gist[1]
>>> or in bpaste[2].
>>>
>>> My daughter was born 4 days ago, so it might be a while till I am able
>>> to look into the code, but I will do it asap.
>>>
>>>
>>> [1] https://gist.github.com/
>>> [2] https://bpaste.net/
>>>
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Ok, thakns. I had already added  demot that is quite similar to ours.
Let me know if you think yours adds soemthing special that I did not
noticed.
The algorithm of the two functions is the same. You calculate the
distance between a given point and all the segments of the polyline.
Then you return this distance and the orthogonal projection on that
segment. This is brute force search, and there is little else you can
do unless you want to implement octrees or another data structure that
optimizes the search. The difference between the function you sent and
the one in geometry is that the computation of the distance and
projection on the edge is encapsulated in the function
distancePointEdge. This last function has some optimizations on it
that use broadcast instead of looping, but feel free to profile it and
check if there is anything to improve.

If you port the Scilab function it should perform similarly.

What is your problem exactly? Do you have many points and a single
polyline or your have a massive polyline and a few points (compared
with the number of vertices of the polyline)?

If you have many points and a fixed polyline, look at the demo I added
to the function. It uses arrayfun and calls the function for each
point (this prevents one of the nested loops within the function, and
it cloud be improved to do this by default). If your polyline has many
segments then I can provide a function that uses arrayfun for the
looping of the edges.