Dear all,

I would like to calculate a distance as follows: distance is defined as the straight-line distance between a survey cluster and the origin of the event. The point location of a survey cluster is determined by the longitude and latitude of each survey cluster. The origin of the event is assumed to be the middle point of country CM whose latitude and longitude is (−6.31, 23.59). Any help is much appreciated. Thank you.
Code:
clear
input str2 country int cluster double(latnum longnum)
"BF"  1 12.3667 -1.5167
"BF"  2 15.4567 -2.6167
"BF"  3 20.1235 -0.6167
"BF"  4 5.2346 -8.2314
"BF"  5 6.1676 -5.4177
"CM"   1  4.0526  9.7240
"CM"   2  9.1209 13.5651
"CM"   3 10.3284 15.2224
"CM"   4 12.7535 14.5469
"CM"   5  4.5154 10.2928
"ET"  1 11.0753 20.3376
"ET"  2 9.14200 18.3946
"ET"  3 12.2618 16.5945
"ET"  4 7.8851  17.04987
"ET"  5 13.0943 27.4918
"GH"  1    5.1 -3.0833
"GH"  2 5.0833   -2.55
"GH"  3 4.9667 -2.3833
"GH"  4 5.0167 -2.1667
"GH"  5 4.8833    -1.9
"GN" 1101 6.9544 -13.8085
"GN" 1102 9.6652 -12.5995
"GN" 1103 8.6687 -11.5976
"GN" 1104 5.7362 -9.5834
"GN" 1105 3.9242 -8.2895
"ML"   1 9.5884 -10.895643
"ML"   2 10.4519 -11.43128
"ML"   3 7.4345 -11.441427
"ML"   4 12.8021 -10.85005
"ML"   5 15.6098 -9.034747
"MW" 1001 -9.5721 20.3730
"MW" 1002 -6.54736 30.2916
"MW" 1003 -10.8601 43.4302
"MW" 1004 -12.5576 12.4524
"MW" 1005 -15.4934 11.6710
end
la var latnum "latitude"
la var longnum "longitude"