anchor.diff:  "nhd_6866467","swimms","maxdepth",4.572
   "nhd_13290832","swimms","maxdepth",27.432
   "nhd_13104083","swimms","maxdepth",10.9728
  +"nhd_13104083","swimms","maxdepth",10.9728
   "nhd_13105835","swimms","maxdepth",1.8288
  -NA,"swimms","maxdepth",2.7432
   "nhd_9035959","swimms","maxdepth",5.1816
  -NA,"swimms","maxdepth",5.4864
   "nhd_13078249","swimms","maxdepth",10.0584
   "nhd_2260757","swimms","maxdepth",3.3528
   "nhd_13394839","swimms","maxdepth",4.572
   "nhd_1849751","swimms","maxdepth",13.716
   "nhd_13118798","swimms","maxdepth",9.144
  -NA,"swimms","maxdepth",2.4384
  -NA,"swimms","maxdepth",23.4696
  -NA,"swimms","maxdepth",16.4592
   "nhd_13104021","swimms","maxdepth",9.4488
   "nhd_14726496","swimms","maxdepth",6.096
  -NA,"swimms","maxdepth",5.1816
   "nhd_1816325","swimms","maxdepth",2.7432
  -"nhd_2646946","swimms","maxdepth",NA
  -NA,"swimms","maxdepth",9.144
   "nhd_14726182","swimms","maxdepth",6.096
   "nhd_13345562","swimms","maxdepth",6.4008
   "nhd_2261037","swimms","maxdepth",1.2192
  -NA,"swimms","maxdepth",2.4384
   "nhd_13394167","swimms","maxdepth",11.8872
  -NA,"swimms","maxdepth",NA
   "nhd_13395071","swimms","maxdepth",10.3632
   "nhd_6816830","swimms","maxdepth",7.3152
  -NA,"swimms","maxdepth",4.572
   "nhd_9032833","swimms","maxdepth",8.5344
  -NA,"swimms","maxdepth",2.1336
   "nhd_13343196","swimms","maxdepth",16.764
   "nhd_14726642","swimms","maxdepth",1.8288
   "nhd_2643950","swimms","maxdepth",3.6576
   "nhd_13395117","swimms","maxdepth",7.3152
   "nhd_2647096","swimms","maxdepth",4.2672
   "nhd_13391575","swimms","maxdepth",2.4384
  -NA,"swimms","maxdepth",3.048
   "nhd_13120882","swimms","maxdepth",9.7536
   "nhd_13078117","swimms","maxdepth",6.7056
  -NA,"swimms","maxdepth",3.9624
  -NA,"swimms","maxdepth",2.1336
   "nhd_13343634","swimms","maxdepth",5.1816
   "nhd_13294494","swimms","maxdepth",4.8768
   "nhd_9035945","swimms","maxdepth",12.192
  
positive.code: "nhd_120052158","swimms","maxdepth",6.096
  "nhd_1849485","swimms","maxdepth",14.3256
  "nhd_13395123","swimms","maxdepth",6.7056
  NA,"swimms","maxdepth",5.4864
  NA,"swimms","maxdepth",1.8288
  "nhd_1855167","swimms","maxdepth",2.1336
  "nhd_12990945","swimms","maxdepth",4.8768
  NA,"swimms","maxdepth",1.8288
  "nhd_13395085","swimms","maxdepth",7.0104
  "nhd_13349598","swimms","maxdepth",3.9624
  "nhd_1816119","swimms","maxdepth",10.9728
  
negative.code: "nhd_13290756","swimms","maxdepth",1.2192
  "nhd_13078787","swimms","maxdepth",7.62
  "nhd_12980603","swimms","maxdepth",3.048
  "nhd_2266383","swimms","maxdepth",0.9144
  "nhd_14707904","swimms","maxdepth",2.4384
  "nhd_12980661","swimms","maxdepth",2.4384
  "nhd_6819970","swimms","maxdepth",8.5344
  "nhd_13290764","swimms","maxdepth",2.4384
  "nhd_14783899","swimms","maxdepth",7.0104
  "nhd_6842315","swimms","maxdepth",8.2296
  