This set of the commands is purposed to manage subdirectories. The directory system have the same principle as in file systems. Directories can be created by the command md and they can be removed by the command rd. The NDA kernel maintains the current working directory which can be changed by the command cd.
Subdirectories should always be created by the command md, but items can be referred by giving the whole or relative path name to an entry, for instance, "/tmp/data" or "tmp/data".
The following examples demonstrate some cases which can be more useful to manage by splitting information processing to distinct directories.
Example: Because the Boston data has 14 fields, it is clearer to hide fields under the directory "bostondir". Note that only one level of the new directories can be created at a time by the command md.
# load data to the directory "data" NDA> md bostondir NDA> cd bostondir NDA> load boston.dat NDA> cd .. NDA> ls bostondir
The Boston data is loaded to the root directory "/". Then it is preprocessed and the results are stored in the different subdirectory "process1".
# load data to the root directory NDA> pwd / NDA> load boston.dat NDA> md process1 # preprocess the data and store results in a subdirectory NDA> prepro -d boston -dout process1/data -e -n ...
It is clear that the analyzing process uses only data which have been got by selecting low-priced apartments by the command selrec (see Sect. 4.2.3). Then the analyzing process of this data is isolated to its own directory "phase2" as the following commands show.
... # select a part of the data from the boston data NDA> md phase2 NDA> selrec -d boston -expr 'boston.rate' < 40; -dout phase2/data NDA> cd phase2 # data analysis for low-priced apartments ...
References to name entries in different directories can be given as an absolute or relative path to the current working directory. The example shows also that only an empty directory can be removed.
... # references to name entries in different directories NDA> ls ../bostondir -fr * boston boston.crim boston.zn ... NDA> somtr -d ../bostondir/boston -sout som1 -l 4 NDA> cd .. NDA> rd bostondir -134 Try to remove a directory that is not empty # Error caused by the deletion of the non-empty subdirectory. # Thus let's remove items under it firstly NDA> rm bostondir/boston NDA> rd bostondir ...