1 item has been added to your cart.

Data management

1. Stata 10 has new date/time variables, so you can now record values like 14jun2007 09:42:41.106 in one variable. They are called %tc and %tC variables. The first is unadjusted for leap seconds; the second is adjusted.
   
   What used to be called “daily variables” are now called %td variables. This is just a jargon change; daily (%td) variables continue to work as they did before—0 means 01jan1960, 1 means 02jan1960, and so on.
   
   %tc and %tC variables work similarly: 0 means 01jan1960 00:00:00. Here, however, 1 means 01jan1960 00:00:00.001, 1000 means 01jan1960 00:00:01.000, and 02jan1960 08:00:00 is 115,200,000. The underlying values are big—so it is important that you store them as doubles—but the %tc and %tC formats make the values readable, just as the %td format makes daily (%td) values readable.
   
   There are many new functions to go along with this new value type. clock(), for instance, converts strings such as “02jan1960 08:00:00” (or even “8:00 a.m., 1/2/1960”) to their numeric equivalents. dofc() converts a %tc value (such as 115,200,000, meaning 02jan1960 08:00:00) to its %td equivalent (namely, 1, meaning 02jan1960). cofd() does the reverse (the result would be 86,400,000, meaning 02jan1960 00:00:00).
   
   See [D] dates and times.
2. The previously existing date() function, which converts strings to %td values, is now smarter. In addition to being able to convert strings such as “21aug2005”, “August 21, 2005”, it can convert “082105”, “08212005”, “210805”, and “21082005”. See [D] dates and times.
3. New command datasignature allows you to sign datasets and later use that signature to determine whether the data have changed. An early version of the command was made available during the Stata 9 release. That command is now called _datasignature and was used as the building block for the new, improved datasignature. See [D] datasignature and [P] _datasignature.
4. Existing command clear now clears data and value labels only. Type “clear all” to clear everything. This change will bite you the first few times you type “clear” expecting it to “clear all”. The problem was that new users were surprised when “clear” by itself cleared everything, whereas “use filename clear” loaded new data and value labels but left everything else in place. The new users were right.
   
   clear now has the following subcommands:
   
   
   1. clear all clears everything from memory.
   2. clear ado clears automatically loaded ado-file programs.
   3. clear programs clears all programs, automatically loaded or not.
   4. clear results clears saved results.
   5. clear mata clears Mata functions and objects from memory.
   See [D] clear.
5. Stata for Unix now supports unixODBC [sic], making it easier to connect to databases such as Oracle, MySQL, and PostgreSQL; see [D] odbc.
6. Existing command describe now allows option varlist that was previously allowed only by describe using. Existing command describe using varlist now allows option simple that was previously only allowed by describe. Option varlist saves the variable names in r(varlist) and optoin simple displays the variable name in a compact form. See [D] describe.
7. Existing command collapse now supports four additional stats: first, the first value; last, the last value; firstnm, the first nonmissing value; and lastnm, the last nonmissing value. See [D] collapse.
8. Existing command cf (compare files) now provides a detailed listing of observations that differ when the verbose option is specified. Setting version to less than 10.0 restores the earlier behavior. See [D] cf.
9. Existing command codebook has new option compact that produces more compact output. See [D] codebook.
10. Existing command insheet has new option case that preserves the case of variable names when importing data; see [D] insheet.
11. Existing command outsheet has new option delimiter() that specifies an alternative delimiter; see [D] outsheet.
12. Existing commands infile and infix can now read up to 524,275 characters per line; the previous limit was 32,765. See [D] infile and [D] infix (fixed format).
13. Existing commands icd9 and icd9p have now been updated to use the V24 codes; see [D] icd9.
14. New function itrim() returns the string with consecutive, internal spaces collapsed to one space; see String functions in [D] functions.
15. New functions lnnormal() and lnnormalden() provide the natural logarithm of the cumulative standard normal distribution and of the standard normal density; see Probability distributions and density functions in [D] functions.
16. New functions for calculating cumulative densities are now available:

    binomial(n, k, p)	lower tail of the binomial distribution
    ibetatail(a, b, x)	reverse (upper tail) of the cumulative beta distribution
    gammaptail(a, x)	reverse (upper tail) of the cumulative gamma distribution
    invgammaptail(am p)	inverse reverse of the cumulative gamma distribution
    invibetatail(a, b, p)	inverse reverse of the cumulative beta distribution
    invbinomialtail(n, k, p)	inverse of right cumulative binomial

    See Probability distributions and density functions in [D] functions.

17. Existing function Binomial(n, k, p) has been renamed binomialtail(n, k, p), thus making its name consistent with the naming convention for probability functions. The accuracy of the function has also been improved for very large values of n. At the other end of the number line, the function now returns the appropriate 0 or 1 value when n = 0, rather than returning missing. Binomial() continues to work as a synonym for binomialtail().
18. The behavior and accuracy of the following probability functions have been improved:
    
    
1. F(n₁, n₂, f) and Ftail(n₁, n₂, f) are more accurate for small values of n₁ and large values of n₂. Also, F() is more accurate for large f where n₁ and n₂ are less than 1.
2. gammap(a, x) is more accurate when a is large and x is near a.
3. ibeta(a, b, x) now is more accurate when x is near a/(a + b) and a or b is large.
4. invbinomial(n, k, p), invchi2(n, p), invchi2tail(n, p), invF(n₁, n₂, p), and invgammap(a, p) are more accurate for small values of p or for returned values close to zero.
5. invFtail(n₁, n₂, p) and invibeta(a, b, p) are more accurate for small values of p or for returned values close to zero.
6. invttail(n, p) is more accurate for small values of p or for returned values close to zero.
7. ttail(n, t) is more accurate for exceedingly large values of n.
19. Existing function invbinomial(n, k, p) now returns the probability of a success on one trial such that the probability of observing k or fewer successes in n trials is p. The previous behavior of invbinomial() is restored under version control.
20. New function fmtwidth() returns the display width of a %fmt string; see Programming functions in [D] functions.
21. The maximum length of a %fmt has increased from 12 to 48 characters; see [D] format. (This change was necessitated by the new date/time variables).
22. Existing commands corr2data and drawnorm now allow singular correlation (or covariance) structures. New option forcepsd modifies a matrix to be positive semidefinite and thus to be a proper covariance matrix. See [D] corr2data and [D] drawnorm.
23. Existing command hexdump analyze now saves the number of \r\n characters in r(Windows) rather than in r(DOS). r(DOS) is still set when version is less than 10. See [D] hexdump.

Back to highlights