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My first custom function--the haversine formula

my first post and a chance to say how useful i have found this site and the linked videos 
I have recently been tasked with testing how far customers laddresses are from the business. I found a data base which had the longitude and latitude of every UK postcode,  armed with that information i came up with this custom function
Option ExplicitFunction getDistance(latitude1 As Double,longitude1 As Double,latitude2 As Double,longitude2 As Double) As DoubleDim earth_radius As DoubleDim Pi As DoubleDim deg2rad As Double
Dim dLat As DoubleDim dLon As DoubleDim a As DoubleDim c As DoubleDim d As Double
earth_radius = 6371Pi = 3.14159265deg2rad = Pi / 180
dLat = deg2rad * (latitude2 - latitude1)dLon = deg2rad * (longitude2 - longitude1)
a = Sin(dLat / 2) * Sin(dLat / 2) + Cos(deg2rad * latitude1) * Cos(deg2rad * latitude2) * Sin(dLon / 2) * Sin(dLon / 2)c = 2 * Sqr(Atn(a / Sqr(1 - (a*a))))
d = earth_radius * c
getdistance = d
End Function
I couldn't have done with out the help of the Youtube videos on custom functioms and a little help with the  trigonometery  from Google

Brian Element Wed, 12/01/2021 - 09:59

Hey Michael, that is great to hear.  Thanks for sharing the code.  I hate to break it to you but there was one that already did this in passport which I have attached.  You can have a look and hopefully it gives the same results as yours.

Thanks for letting me know.  It gives me incentives to keep creating videos and adding information to the site.

Michael Davey Wed, 12/01/2021 - 10:25

well mine is in kilometers...
Its more satisfying to write your own code particulary when its my first time in IDEA. I have learned few things looking at the passport version as well so its all good.
keep up the good work!

Brian Element Wed, 12/01/2021 - 10:31

Yes it is.  I find it fun to write code.  Kind of like putting a puzzle together.  Keep writing those functions.