anchor.diff:  "nhd_13393885","swimms","maxdepth",6.4008
   "nhd_1813593","swimms","maxdepth",7.0104
   "nhd_1797451","swimms","maxdepth",10.9728
  -"nhd_2644250","swimms","maxdepth",NA
   "nhd_6842389","swimms","maxdepth",16.764
   "nhd_2265939","swimms","maxdepth",8.5344
   "nhd_2265893","swimms","maxdepth",3.048
  -NA,"swimms","maxdepth",3.6576
  +"nhd_13119476","swimms","maxdepth",3.6576
   "nhd_13394845","swimms","maxdepth",2.4384
   "nhd_13343900","swimms","maxdepth",12.4968
  -NA,"swimms","maxdepth",3.3528
  -"nhd_2266115","swimms","maxdepth",NA
  +"nhd_1855077","swimms","maxdepth",1.2192
  +"nhd_1852005","swimms","maxdepth",1.2192
  +"nhd_1852019","swimms","maxdepth",1.2192
   "nhd_1852019","swimms","maxdepth",1.2192
   "nhd_6819506","swimms","maxdepth",6.096
  -NA,"swimms","maxdepth",5.1816
  -NA,"swimms","maxdepth",2.1336
   "nhd_14701606","swimms","maxdepth",7.0104
   "nhd_13393449","swimms","maxdepth",6.096
   "nhd_1813385","swimms","maxdepth",7.62
  -NA,"swimms","maxdepth",10.668
   "nhd_13078599","swimms","maxdepth",3.3528
  -NA,"swimms","maxdepth",4.572
   "nhd_13120944","swimms","maxdepth",3.9624
  -NA,"swimms","maxdepth",6.7056
   "nhd_1850167","swimms","maxdepth",3.048
   "nhd_2644320","swimms","maxdepth",1.8288
   "nhd_13079071","swimms","maxdepth",4.2672
  -NA,"swimms","maxdepth",4.8768
   "nhd_13121292","swimms","maxdepth",5.4864
   "nhd_13394495","swimms","maxdepth",5.4864
   "nhd_13062689","swimms","maxdepth",1.524
  
positive.code: "nhd_12988303","swimms","maxdepth",10.3632
  "nhd_9036273","swimms","maxdepth",5.1816
  "nhd_12161108","swimms","maxdepth",14.3256
  NA,"swimms","maxdepth",NA
  NA,"swimms","maxdepth",1.8288
  "nhd_13293226","swimms","maxdepth",NA
  NA,"swimms","maxdepth",1.8288
  "nhd_13394501","swimms","maxdepth",9.144
  "nhd_13394077","swimms","maxdepth",25.6032
  "nhd_1852763","swimms","maxdepth",10.668
  
negative.code: "nhd_9032811","swimms","maxdepth",4.572
  "nhd_14726186","swimms","maxdepth",4.2672
  "nhd_9028505","swimms","maxdepth",1.2192
  "nhd_13121024","swimms","maxdepth",2.7432
  "nhd_13394313","swimms","maxdepth",3.6576
  "nhd_13079077","swimms","maxdepth",3.6576
  "nhd_2265981","swimms","maxdepth",15.24
  "nhd_13395045","swimms","maxdepth",4.2672
  "nhd_13393881","swimms","maxdepth",18.288
  "nhd_1849725","swimms","maxdepth",6.4008
  "nhd_6791945","swimms","maxdepth",8.2296
  "nhd_1813415","swimms","maxdepth",5.1816
  "nhd_13395185","swimms","maxdepth",4.8768
  "nhd_14708610","swimms","maxdepth",5.7912
  "nhd_14708604","swimms","maxdepth",5.7912
  "nhd_2113606","swimms","maxdepth",2.1336
  "nhd_6842935","swimms","maxdepth",5.4864
  "nhd_1797431","swimms","maxdepth",14.6304
  "nhd_1816285","swimms","maxdepth",6.4008
  "nhd_13345688","swimms","maxdepth",2.1336
  