pc_flip.md
In nzilbb.vowels: Vowel Covariation Tools

`pc_flip` results unchanged for onze_intercepts.

Code
  pc_flip(pca_obj, pc_no = 3, flip_var = "F1_GOOSE")
Output
  Standard deviations (1, .., p=20):
   [1] 1.9121981 1.6889048 1.4067436 1.2926631 1.2442912 1.1257951 1.0107303
   [8] 0.9399614 0.9224174 0.9096253 0.8072463 0.7531132 0.6899545 0.6630649
  [15] 0.6225829 0.5762850 0.4939469 0.4186780 0.3407660 0.2291614

  Rotation (n x k) = (20 x 20):
                     PC1         PC2         PC3         PC4         PC5
  F1_DRESS   -0.16484537  0.23077454 -0.10669169 -0.25388597  0.12674908
  F2_DRESS   -0.19193722 -0.32982354  0.02011533 -0.24993249 -0.16188370
  F1_FLEECE   0.30104237 -0.22277760  0.23376198 -0.02683929  0.21115386
  F2_FLEECE  -0.31184889  0.06446611  0.32666875  0.14488444 -0.12754932
  F1_GOOSE    0.26881473 -0.15386567  0.26867319  0.31889632  0.00628898
  F2_GOOSE    0.13962618  0.16084318 -0.41331089 -0.14381043  0.13743095
  F1_KIT      0.10840805 -0.04508250 -0.25036329 -0.38007922 -0.22652613
  F2_KIT     -0.07375636  0.35040789 -0.01338551  0.15640478  0.33019576
  F1_LOT     -0.15220984 -0.09111831 -0.13638109  0.48220571 -0.26387197
  F2_LOT     -0.06514777  0.30964236  0.37593842 -0.03322567 -0.11402799
  F1_NURSE   -0.05280471  0.28085633 -0.05246158 -0.22897391 -0.02275139
  F2_NURSE    0.30467952  0.06452547 -0.31075059  0.19913744  0.22367229
  F1_START    0.36795231 -0.05411997  0.24806114 -0.06724662  0.33250311
  F2_START    0.11880891  0.22855335  0.16019542 -0.01746827 -0.28597263
  F1_STRUT    0.20643295 -0.13434271 -0.22979021  0.03728346 -0.46316275
  F2_STRUT    0.18833004  0.29250134  0.08776909  0.09997773 -0.32677128
  F1_THOUGHT -0.30368608 -0.08188486 -0.21356445  0.22072029  0.09918089
  F2_THOUGHT -0.28674913 -0.33009061 -0.09206115  0.13993673  0.21002639
  F1_TRAP    -0.33624907  0.08643406  0.15379859 -0.19954169  0.12570436
  F2_TRAP     0.03208969 -0.37507249  0.19050580 -0.33169912 -0.03222288
                     PC6          PC7           PC8         PC9        PC10
  F1_DRESS   -0.36596436 -0.404350867  0.3409572888 -0.14599090  0.08795220
  F2_DRESS   -0.02348528 -0.182528771 -0.0792093250 -0.06614411 -0.09221578
  F1_FLEECE  -0.18788774 -0.012769484 -0.0048077269  0.29467825 -0.05295878
  F2_FLEECE   0.13016143  0.229199737  0.1553789818 -0.17628939  0.28415343
  F1_GOOSE   -0.02604364 -0.024409423 -0.0002887154 -0.36422993  0.18298285
  F2_GOOSE    0.12557628  0.370844406  0.0639396509  0.17265494  0.38669348
  F1_KIT     -0.23532537  0.241363617 -0.4822891069 -0.21928844 -0.17418515
  F2_KIT     -0.05406068 -0.419030429 -0.1349194525 -0.11449845 -0.20059422
  F1_LOT     -0.05256598 -0.094550956 -0.0845901162  0.47982148  0.09141792
  F2_LOT      0.00994633  0.070615185 -0.4122727052 -0.20121492  0.06695512
  F1_NURSE    0.63074379 -0.020225159  0.2014310190 -0.01406214 -0.11786577
  F2_NURSE   -0.05514555 -0.126786373 -0.1630866956 -0.02742337  0.06188892
  F1_START    0.09637902  0.179163384  0.0827503751 -0.05158468 -0.07101176
  F2_START   -0.44442033  0.257729872  0.4044551353  0.05272796 -0.23401372
  F1_STRUT    0.04429550 -0.273629278  0.1530420052 -0.29625310  0.26318783
  F2_STRUT    0.20053220 -0.151953305 -0.2105507443  0.22885955 -0.33802294
  F1_THOUGHT -0.05545046  0.315421635  0.1614235481 -0.10099434 -0.48411523
  F2_THOUGHT  0.10882424  0.024753760 -0.1377640564 -0.24287097 -0.10014599
  F1_TRAP    -0.19324799  0.006429305 -0.2387273428  0.30015995  0.33620300
  F2_TRAP     0.18316587 -0.226895658  0.1179218961  0.23705708 -0.12367420
                     PC11        PC12        PC13        PC14          PC15
  F1_DRESS   -0.127717845 -0.06471333 -0.24943840 -0.24808849  0.1121455910
  F2_DRESS    0.543532031  0.27876185  0.02890315  0.33847525  0.3370026294
  F1_FLEECE  -0.368856949  0.21771212 -0.09410886  0.18234492  0.3112501247
  F2_FLEECE  -0.313439697  0.18036501  0.13120612 -0.09123646  0.1843641159
  F1_GOOSE    0.401433836 -0.12385297 -0.11461409 -0.23136984 -0.2694485687
  F2_GOOSE    0.166942913  0.17109692 -0.39855735  0.15555548  0.0016652002
  F1_KIT     -0.072258263  0.01813165  0.05088159 -0.42619345  0.0667086078
  F2_KIT      0.156814610  0.24568812 -0.06881534  0.02696925  0.0120130213
  F1_LOT      0.190668651 -0.08717243 -0.08844935 -0.33106815  0.3422645564
  F2_LOT     -0.028850739 -0.36086412 -0.28633337  0.31815714  0.3144039654
  F1_NURSE    0.126930867 -0.07983401  0.27849707 -0.13958773  0.2179184427
  F2_NURSE   -0.071619903 -0.33646052  0.52192582  0.21546668  0.1852502725
  F1_START    0.183298648  0.16903774  0.01156378 -0.10983805  0.0734740871
  F2_START    0.180625787  0.06370424  0.31237442  0.07398928  0.0515442952
  F1_STRUT   -0.184066612  0.10816911  0.01561498  0.33027943 -0.1101060888
  F2_STRUT   -0.134630573  0.31586187 -0.11348484  0.04271514 -0.3234019200
  F1_THOUGHT -0.008456574 -0.25307554 -0.20447315  0.29694832 -0.1571990306
  F2_THOUGHT -0.195631617  0.30753650  0.12736713 -0.07692717  0.0006535444
  F1_TRAP     0.123643123  0.01875710  0.33379267  0.14336921 -0.4411752560
  F2_TRAP    -0.069580547 -0.41519714 -0.10725733 -0.04874113 -0.1544998485
                     PC16        PC17        PC18        PC19       PC20
  F1_DRESS   -0.390932648  0.03083423  0.03251829 -0.01958299 0.26994167
  F2_DRESS   -0.212155048  0.15329542 -0.15173510  0.13368140 0.02770723
  F1_FLEECE   0.050965470 -0.32930836 -0.37500680 -0.08624629 0.23047338
  F2_FLEECE   0.080092118  0.39703066 -0.22650615  0.32620531 0.19265265
  F1_GOOSE   -0.110893018 -0.26950352 -0.28350388  0.15514390 0.23998098
  F2_GOOSE    0.049021724 -0.07917520  0.07543701  0.34358233 0.18684444
  F1_KIT      0.180119396  0.06411682 -0.15961382  0.01327473 0.21600346
  F2_KIT      0.597083696  0.05887740 -0.05057835  0.16865336 0.08065294
  F1_LOT      0.079587927  0.03331831  0.13751634 -0.13705387 0.25820099
  F2_LOT     -0.030487525 -0.14590389  0.27423424 -0.04467554 0.10900942
  F1_NURSE    0.013537120 -0.33675588 -0.18635537 -0.17788642 0.25048507
  F2_NURSE   -0.219172663  0.18056277 -0.01961511  0.29110286 0.17090975
  F1_START   -0.028629739  0.45886333  0.36003888 -0.35845772 0.28260186
  F2_START    0.138951491 -0.22992049  0.26342956  0.22332337 0.08370600
  F1_STRUT    0.270626796  0.02249697  0.11398396 -0.29403501 0.27038274
  F2_STRUT   -0.391935338  0.11063294  0.00484196  0.18770904 0.20476365
  F1_THOUGHT  0.001243774  0.12331559 -0.21901107 -0.14938477 0.34555352
  F2_THOUGHT -0.130910100 -0.38874131  0.49613996  0.16545391 0.19854072
  F1_TRAP     0.012179706 -0.05043020 -0.04287974 -0.20587463 0.33693619
  F2_TRAP     0.264096595  0.09774491  0.18071362  0.40971089 0.21378920