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From |
"Scott Merryman" <[email protected]> |

To |
[email protected] |

Subject |
st: R Array [was: Mata for data management] |

Date |
Fri, 1 Feb 2008 09:02:25 -0600 |

Thanks. I guess, more concretely, what can be done (or preformed more efficiently) with an R array that cannot be done with Stata (-foreach- or -forv-)? Scott On Jan 31, 2008 9:44 PM, Gabi Huiber <[email protected]> wrote: > Oops. Thank you, Scott. > > An array is a general data object. It's a a vector when indexed by one > subscript, a matrix when indexed by two subscripts, or it can be > indexed by more than two subscripts. It can take numeric and character > elements. You can think of a numeric array A(i,j,k) as a list of i > matrices of (j,k) size. The ability to take non-numeric elements is > useless in statistics, but it's helpful in general data management. > > In Stata or SAS we think of data sets as tables with as many columns > as variables and as many rows as the largest number of non-missing > observations. This works for statistical analysis. General-purpose > programming languages (judging by the two I dabble in) seem to want > you to think of your data in terms of data objects -- scalars, > vectors, matrices, lists, etc. R is a statistical analysis programming > environment, but it stayed close to this general-purpose way of > dealing with data; maybe because its underlying language, S, was > invented by a computer scientist? > > Gabi > > > On Jan 31, 2008 10:14 PM, Scott Merryman <[email protected]> wrote: > > On Jan 31, 2008 8:48 PM, Gabi Huiber <[email protected]> wrote: > > > I'm trying to cheat and speed things up a bit when dealing with a > > > bunch of files with names such as fileYYYYMMDD.dta. I could collect > > > the numeric part of the names in a column vector that starts with the > > > initial values a=J({potential number of files}, 1,0). But there is a > > > fair chance that my YYYYMMDD succession has gaps, so at the end of the > > > process this column vector will have some zeroes. > > > > > > I would like to do this: > > > > > > mata > > > a=sort(a,1) > > > > > > Then drop all the zero elements of a, and end up with a shorter > > > vector. But I can't find anything like "drop rows" in the Mata book or > > > Google. Any ideas? > > > > -select()- ? > > > > mata > > A = (1,2,3,4,0,5,6,0,0,7) > > A2 = select(A, A:>0) > > A2 > > end > > > > > > > Generally, some R-like way to deal with arrays would be nice to have > > > in Mata or Stata. > > > > How do R arrays work? > > > > Scott > > > > > * > > * For searches and help try: > > * http://www.stata.com/support/faqs/res/findit.html > > * http://www.stata.com/support/statalist/faq > > * http://www.ats.ucla.edu/stat/stata/ > > > * > * For searches and help try: > * http://www.stata.com/support/faqs/res/findit.html > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: R Array [was: Mata for data management]***From:*"Gabi Huiber" <[email protected]>

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