[U] User's Guide

114 [ U ] 11 Language syntaxBy typing this, we want to create new variable finalval, which contains, in each observation, thefinal observed value of val for each subject in the data. The final value will be the last value if,within subject, the data are sorted by time. The above command verifies that the data are sorted bysubject and time and then, if they are, performs. by subject: gen finalval = val[_N]If the data are not sorted properly, an error message will instead be issued. Of course, we could havejust typed. by subject: gen finalval = val[_N]after verifying for ourselves that the data were sorted properly, as long as we were careful to look.by’s second syntax can be used with by’s sort option, so we can also type. by subject (time), sort: gen finalval = val[_N]which is equivalent to. sort subject time. by subject: gen finalval = val[_N]11.6 File-naming conventionsSome commands require that you specify a filename. Filenames are specified in the way naturalfor your operating system:Windows Unix Macmydata mydata mydatamydata.dta mydata.dta mydata.dtac:mydata.dta ~ friend/mydata.dta ~ friend/mydata.dta"my data" "my data" "my data""my data.dta" "my data.dta" "my data.dta"myproj\mydata myproj/mydata myproj/mydata"my project\my data" "my project/my data" "my project/my data"C:\analysis\data\mydata"C:\my project\my data"~ /analysis/data/mydata ~ /my project/my data" ~ /analysis/data/mydata~ /my project/my data"..\data\mydata ../data/mydata ../data/mydata"..\my project\my data" "../my project/my data" "../my project/my data"In most cases, where filename is a file that you are loading, filename may also be a URL. Forinstance, we might specify use http://www.stata-press.com/data/r11/nlswork.Usually (the exceptions being copy, dir, ls, erase, rm, and type), Stata automatically providesa file extension if you do not supply one. For instance, if you type use mydata, Stata assumes thatyou mean use mydata.dta because .dta is the file extension Stata normally uses for data files.