Math lib (even in C or C++... nobody is perfect !)

ruby-talk
1

I am looking for a function to calculate the barycentre of a point list (GPS coordinates lat/lng) ..

anybody aware of such lib or utility I could rewrite in Ruby ? bet it doesn't exist yet

thanks for any hint
joss

2

Hi!

Whenever I need to use a math lib in C, I use the GNU Scientific Library (GSL): GSL - GNU Scientific Library - GNU Project - Free Software Foundation
However, no idea if it contains what you need...

cheers, Severin

Josselin schrieb:

···

I am looking for a function to calculate the barycentre of a point list (GPS coordinates lat/lng) ..

anybody aware of such lib or utility I could rewrite in Ruby ? bet it doesn't exist yet

thanks for any hint
joss

3

got it from a PHP script.. translated into Ruby...

def deg2rad(d)
    (d/180.0)*Math::PI
end
def rad2deg(r)
    (r/Math::PI)*180
end

def self.gravity_center(placemarks)
  sumx = 0.0
  sumy = 0.0
  sumz = 0.0

  for placemark in placemarks do
          # convert to radians
          lat = deg2rad(placemark[0])
          lon = deg2rad(placemark[1])
          # convert spherical coordinate into cartesian
          x = Math::cos(lat) * Math::sin(lon)
          y = Math::cos(lat) * Math::cos(lon)
          z = Math::sin(lat)
          # sum the vectors
          sumx += x
          sumy += y
          sumz += z
  end

  # convert cartesian coordinate back to spherical
  meanz = sumz / placemarks.nitems
  lon = rad2deg(Math::atan2(sumx, sumy))

  meanx = sumx / placemarks.nitems
  meany = sumy / placemarks.nitems
  lat = rad2deg(Math::atan(meanz / Math::sqrt(meanx**2 + meany**2)))
  return [lat, lon]
end

···

On 2007-05-18 15:38:27 +0200, Severin Schoepke <severin.schoepke@gmail.com> said:

Hi!

Whenever I need to use a math lib in C, I use the GNU Scientific Library (GSL): GSL - GNU Scientific Library - GNU Project - Free Software Foundation
However, no idea if it contains what you need...

cheers, Severin

Josselin schrieb:

I am looking for a function to calculate the barycentre of a point list (GPS coordinates lat/lng) ..

anybody aware of such lib or utility I could rewrite in Ruby ? bet it doesn't exist yet

thanks for any hint
joss