· Apr 26 3m read

Geo Vector Search #2

Technical surprises using VECTORs

Building my tech. example provided me with a bunch of findings htt I want to share.
The first vectors I touched appeared with text analysis and more than 200  dimensions.
I have to confess that I feel well with Einstein's 4 dimensional world.
7 to 15 dimensions populating the String Theory are somewhat across the border.
But 200 and more is definitely far beyond my mathematical horizon.

So I looked to our Globe and found a vector of (latitude,longitude) with 2 dimension is enough for testing.
A handy table of capitals was found and provided sample test data (shortened).

Kabul Afghanistan 34.28N 69.11E
Tirana Albania 41.18N 19.49E
Algiers Algeria 36.42N 03.08E
Pago Pago American Samoa 14.16S 170.43W
Andorra la Vella Andorra 42.31N 01.32E
Luanda Angola 08.50S 13.15E
Saint John's Antigua and Barbuda 17.127N 61.846W
Buenos Aires Argentina 36.30S 60.00W
Yerevan Armenia 40.10N 44.31E
Oranjestad Aruba 12.32N 70.02W
Canberra Australia 35.15S 149.08E
Vienna Austria 48.12N 16.22E
Baku Azerbaijan 40.29N 49.56E
Nassau Bahamas 25.05N 77.20W
Manama Bahrain 26.10N 50.30E
Dhaka Bangladesh 23.43N 90.26E
Bridgetown Barbados 13.05N 59.30W
Minsk Belarus 53.52N 27.30E
Brussels Belgium 50.51N 04.21E

 Loading that TAB separated text file with LOAD DATA (SQL) worked perfect

Transforming the geo coordinates int INT was a minor coding exercises
It resulted in a ClassMethod projected as SQL Procedure used inana UPDATE over the table.

As geo coordinates refer to (0°N,0°W) somewhere in the Atlantic this is just a theoretical base for my vectors.
IRIS supports some VECTOR functions but I found no AddVector() or SubtractVector() function.
so this was done "manually" from the input coordinates.
The need arises from transforming coordinates to a useful base point for later comparing vectors
So you see static BASE coordinates and active WORK coordinates.

Getting the Vector's values is easy with SQL using %EXTERNAL() function
while in ObjectScript I ended up with
        set vectorvalues=##class(%Vector).LogicalToOdbc(vectorvariable) 
this was less impressive for working with Vectors.

Similarity is calculated with VECTOR_COSINE() function.
You calculate the angle between 2 Vectors and COSINE norm it between +1 and -1
The input needs 2 Vectors of the same type and same dimension.
Examples as in documentation work fine if you compose your SQL String as suggested
and TO_VETOR(?,type,size) is OK  with  %SQLStatement  for execution.
I tried it with embedded SQL.
Code checking signalled some disagreement but compiled without problem
At runtime it turned out that host variables in TO_VECTOR(:myvec,INT,2) failed
whatever combination of quotes, braces, .... I tried.
So be warned. I returned to  %SQLStatement to get my VCOS done.

     set myvec="1314,-7979" 

Nothing special: Just a plain String with comma-separated values
It seems I couldn't believe that simple approach.
My apologizes to ISC Engineering.

It was a surprise to learn how wide VECTOR_COSINE is spreading.
checking the vector Paris >> Bucuresti  traced half of Middle and East Asia.
So limiting the results to > 0.999 is a good practice in this scenario.



Discussion (4)1
Log in or sign up to continue

I just discovered in class code a different way to get Vector Values from object

USER>set obj=##class(AG.GEO).%OpenId(13)
USER>write obj.VBASE
USER>zwrite obj.VBASE
{"type":"integer", "count":2, "length":2, "vector":[4812,-1622]}  ; <VECTOR>
;;; THIS  is from the generated code
USER>set vec=obj.VBASELogicalToOdbc(obj.VBASE)