Other things related to cm data: [[,cm-method,
[[<-,cm-method, as.cm,
cm-class, cm,
plot,cm-method, read.cm,
rotateAboutZ,
summary,cm-method
Other functions that subset oce objects: subset,adp-method,
subset,adv-method,
subset,amsr-method,
subset,argo-method,
subset,coastline-method,
subset,ctd-method,
subset,echosounder-method,
subset,lobo-method,
subset,met-method,
subset,oce-method,
subset,odf-method,
subset,rsk-method,
subset,sealevel-method,
subset,section-method,
subset,topo-method