Dear Stata users,

I have firm-level panel data (merged with patent-level data) with geographical information such as longitude/latitude/county/city/state etc.
With this, I would like to generate clusters or groups, for example, group A that is clustered by all the firms within 1 or 10 mile(s) from reference location.

However, I do not have clear ideas on:
1) how to decide the reference location; and
2) how to generate this kind of cluster by stata or which command should I use (regarding Ripley's spatial K-function of Space-time K-function).

For more information, following is part of my dataset (since my datas are confidential, this is a brief example):
Code:
 * Example generated by -dataex-. For more info, type help dataex clear input int gvkey double year long patent_num str100 city str8 state_code str33 county float(latitude longitude tag)  0 1950 123456 "Charlotte"       "NC" "Mecklenburg"   35.410557  -80.84306 1  0 1950 123456 "Charlotte"       "NC" "Mecklenburg"   35.410557  -80.84306 1  0 1950 123456 "Charlotte"       "NC" "Mecklenburg"   35.410557  -80.84306 1  0 1950 123456 "Charlotte"       "NC" "Mecklenburg"   35.410557  -80.84306 1  0 1950 123456 "Charlotte"       "NC" "Mecklenburg"   35.410557  -80.84306 1  1 1950 123456 "Maumee"          "OH" "Lucas"          41.70798  -83.70683 1  1 1950 123456 "Naperville"      "IL" "DuPage"         41.79007  -88.20559 1  1 1950 123456 "Maumee"          "OH" "Lucas"          41.70798  -83.70683 1  1 1950 123456 "Naperville"      "IL" "DuPage"         41.79007  -88.20559 1  1 1950 123456 "Naperville"      "IL" "DuPage"         41.79007  -88.20559 1  2 1950 123456 "Waukegan"        "IL" "Lake"           42.16139  -88.13834 1  2 1950 123456 "Chicago"         "IL" "Cook"           41.65819  -87.67947 1  2 1950 123456 "Naugatuck"       "CT" "New Haven"      41.28052 -72.874146 1  2 1950 123456 "Waukegan"        "IL" "Lake"           42.16139  -88.13834 1  2 1950 123456 "Downers Grove"   "IL" "DuPage"         41.81107  -88.02453 1  3 1950 123456 "Irving"          "TX" "Dallas"          32.9027   -96.5636 1  3 1950 123456 "Irving"          "TX" "Dallas"          32.9027   -96.5636 1  3 1950 123456 "Irving"          "TX" "Dallas"          32.9027   -96.5636 1  3 1950 123456 "Irving"          "TX" "Dallas"          32.9027   -96.5636 1  3 1950 123456 "Irving"          "TX" "Dallas"          32.9027   -96.5636 1  4 1950 123456 "Memphis"         "TN" "Shelby"          35.0337   -89.9343 1  4 1950 123456 "Blue Bell"       "PA" "Montgomery"      40.3128  -75.32134 1  4 1950 123456 "Blue Bell"       "PA" "Montgomery"      40.3128  -75.32134 1  4 1950 123456 "Blue Bell"       "PA" "Montgomery"      40.3128  -75.32134 1  4 1950 123456 "Memphis"         "TN" "Shelby"          35.0337   -89.9343 1  5 1950 123456 "Dayton"          "OH" "Montgomery"     39.84139  -84.41647 1  5 1950 123456 "New York"        "NY" "New York"       40.74838 -73.996704 1  5 1950 123456 "Schaumburg"      "IL" "Cook"           41.65819  -87.67947 1  5 1950 123456 "Chicago"         "IL" "Cook"           41.65819  -87.67947 1  5 1950 123456 "La Jolla"        "CA" "San Diego"      33.02935 -116.85355 1  6 1950 123456 "Stamford"        "CT" "Fairfield"      41.25555  -73.43528 1  6 1950 123456 "Stamford"        "CT" "Fairfield"      41.25555  -73.43528 1  6 1950 123456 "Stamford"        "CT" "Fairfield"      41.25555  -73.43528 1  6 1950 123456 "Palo Alto"       "CA" "Santa Clara"   37.444324  -122.1497 1  6 1950 123456 "Racine"          "WI" "Racine"         42.69673  -87.90308 1  7 1950 123456 "Hoffman Estates" "IL" "Cook"           41.65819  -87.67947 1  7 1950 123456 "Cleveland"       "OH" "Cuyahoga"       41.45346  -81.92177 1  7 1950 123456 "Pittsburgh"      "PA" "Allegheny"      40.59417  -79.97028 1  7 1950 123456 "Denver"          "CO" "Denver"          39.7507   -104.989 1  7 1951 123456 "Hoffman Estates" "IL" "Cook"           41.65819  -87.67947 1  8 1950 123456 "Culver City"     "CA" "Los Angeles"    34.26187 -118.45866 1  8 1950 123456 "Chicago"         "IL" "Cook"           41.65819  -87.67947 1  8 1950 123456 "Harrisburg"      "PA" "Dauphin"         40.2782  -76.70937 1  8 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1  8 1950 123456 "Chicago"         "IL" "Cook"           41.65819  -87.67947 1  9 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1  9 1950 123456 "Austin"          "MN" "Freeborn"       43.75284  -93.16799 1  9 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1  9 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1  9 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1 10 1950 123456 "Philadelphia"    "PA" "Philadelphia"    40.1162   -75.0141 1 10 1950 123456 "Philadelphia"    "PA" "Philadelphia"    40.1162   -75.0141 1 10 1950 123456 "Philadelphia"    "PA" "Philadelphia"    40.1162   -75.0141 1 10 1950 123456 "Philadelphia"    "PA" "Philadelphia"    40.1162   -75.0141 1 10 1950 123456 "Philadelphia"    "PA" "Philadelphia"    40.1162   -75.0141 1 11 1950 123456 ""                "TX" ""                      .          . 1 11 1950 123456 "Downers Grove"   "IL" "DuPage"         41.81107  -88.02453 1 11 1950 123456 "Buffalo"         "NY" "Erie"             42.834  -78.63425 1 11 1950 123456 "Oak Brook"       "IL" "DuPage"          41.8364  -87.95317 1 11 1950 123456 "White Pine"      "MI" "Ontonagon"      46.73806  -89.17944 1 12 1950 123456 "Brentwood"       "TN" "Davidson"      36.260387  -86.70456 1 12 1950 123456 "Pittsburgh"      "PA" "Allegheny"      40.59417  -79.97028 1 12 1951 123456 "Brentwood"       "TN" "Davidson"      36.260387  -86.70456 1 12 1951 123456 "Pittsburgh"      "PA" "Allegheny"      40.59417  -79.97028 1 12 1952 123456 "Pittsburgh"      "PA" "Allegheny"      40.59417  -79.97028 1 13 1950 123456 "Parsippany"      "NJ" "Morris"          40.8819  -74.62099 1 13 1950 123456 "Saint Paul"      "MN" "Ramsey"         44.96996  -93.08317 1 13 1950 123456 "Clarks Summit"   "PA" "Lackawanna"     41.34319 -75.530136 1 13 1950 123456 ""                ""   ""                      .          . 1 13 1951 123456 "Clarks Summit"   "PA" "Lackawanna"      41.3731   -75.6841 1 14 1950 123456 "Richmond"        "VA" "Richmond city"         .          . 1 14 1950 123456 "Atlanta"         "GA" "DeKalb"        33.888504  -84.28954 1 14 1950 123456 "Atlanta"         "GA" "Fulton"        34.040833   -84.3859 1 14 1950 123456 "Carteret"        "NJ" "Middlesex"      40.33243  -74.56883 1 14 1950 123456 "Richmond"        "VA" "Richmond city"         .          . 1 15 1950 123456 ""                ""   ""                      .          . 1 15 1950 123456 ""                ""   ""                      .          . 1 15 1950 123456 ""                ""   ""                      .          . 1 15 1950 123456 "Dayton"          "OH" "Warren"         39.37145  -84.21078 1 15 1950 123456 ""                ""   ""                      .          . 1 16 1950 123456 "New Britain"     "CT" "Hartford"       41.92608  -72.64576 1 16 1950 123456 "New York"        "NY" "New York"       40.74838 -73.996704 1 16 1950 123456 "Columbus"        "OH" "Franklin"       40.03219  -83.13834 1 16 1950 123456 "New York"        "NY" "New York"       40.74838 -73.996704 1 16 1950 123456 "New York"        "NY" "New York"       40.74838 -73.996704 1 17 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1 17 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1 17 1950 123456 "Philadelphia"    "PA" "Philadelphia"    40.1162   -75.0141 1 17 1950 123456 "Houston"         "TX" "Harris"         30.00409  -95.28248 1 17 1950 123456 "Philadelphia"    "PA" "Philadelphia"    40.1162   -75.0141 1 18 1950 123456 "Upland"          "IN" "Grant"           40.5112  -85.82655 1 18 1950 123456 "El Segundo"      "CA" "Los Angeles"    34.26187 -118.45866 1 18 1950 123456 "El Segundo"      "CA" "Los Angeles"    34.26187 -118.45866 1 18 1950 123456 "Mckeesport"      "PA" "Allegheny"      40.59417  -79.97028 1 18 1950 123456 "Oakland"         "CA" ""                      .          . 1 19 1950 123456 "Yardley"         "PA" "Bucks"          40.57824  -75.21906 1 19 1950 123456 "Yardley"         "PA" "Bucks"          40.57824  -75.21906 1 19 1950 123456 "Yardley"         "PA" "Bucks"          40.57824  -75.21906 1 19 1950 123456 "Yardley"         "PA" "Bucks"          40.57824  -75.21906 1 19 1950 123456 "Cupertino"       "CA" "Santa Clara"   37.444324  -122.1497 1 end
Please note that Patent_num here is different across observations. Due to confidentiality, I just made them identical.


I have tried to search some related literatures on this methods, however, I could not have yet found the clear solutions and codes that I could use.
Sorry if my questions were unclear.
Could someone help me with these issues, please ?


Thank you very much in advance,
A.-C