md | Create a new subdirectory |
<dirname> | name of subdirectory to be created |
rd | Remove a subdirectory |
<dirname> | name of subdirectory to be removed |
cd | Change the current directory |
<dirname> | name of subdirectory to move to |
pwd | Print current working directory |
This set of commands is meant for managing subdirectories. The directory system has the same principle as file systems. Directories can be created with md and they can be removed with rd. The NDA kernel keeps track of the current working directory, which can be changed with cd command.
Subdirectories should always be created with md command, but items can be referred to by giving the whole (absolute) or relative path of the name entry, for instance, /tmp/first/data or ../first/data (if the current working directory is /tmp/second, for instance). A subdirectory needs to be empty before it can be deleted with rd.
Example: Boston data set contains information about appartments sold in Boston, MA during a certain time period. There are lots of properties, which can be used for truly thorough analyses. If one would want to perform a similar analysis for certain parts of the original data set, it can be easily performed with directories and selrec (see section 4.2.3).
NDA> load boston.dat ... # Split boston data into two parts NDA> md part1 NDA> md part2 NDA> selrec -d boston -expr 'boston.rate' < 40; -dout part1/data NDA> selrec -d boston -expr 'boston.rate' >= 40; -dout part2/data NDA> cd part1 NDA> runcmd analysis # Data analysis for low-priced appartments ... NDA> cd ../part2 # Could perform data analysis for more expensive appartments ...
References to name entries in different directories can be made using absolute or relative paths. This example also shows that only an empty directory can be removed.
... # Referencing name entries in different directories NDA> ls ../part1 -fr * data data.crim data.zn ... NDA> cd .. NDA> somtr -d part1/prep -sout som2 -l 4 ... NDA> rd part2 Returned error -134: Try to remove a directory that is not empty # Error caused by the deletion of a non-empty subdirectory. # Thus let's remove items under it first NDA> rm part2/data NDA> rd part2