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From |
Nick Cox <n.j.cox@durham.ac.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Structure for making line by line changes? |

Date |
Fri, 25 Apr 2003 20:17:08 +0100 |

Dan Sabath > I am very new to Stata and am having some difficulty wrapping my brain around Stata's methods of data processing. I would like to be able to process a dataset line by line rather then all at once. I have found many references to the fact that "if" statements don't work as expected and a very good comparison between STATA and SAS which briefly mentions some of the paradigm shifts. > > My question to the group is how would you deal with the line by line processing issue? I need to change each line based on a calulated value that is dependant upon data in that line. > > The "if" qualifier would seem to solve this for some cases, but not when a program has to be called or a really complex comparison has to be done. > > I wrote a "program" to calculate the value based on args passed into it. > "checkfoo" returns a 1 or 0 depending if one of the arglist matches the first arg. > so r(checked) = 1 if `k' or `l' is equal to `j' > otherwise r(checked) = 0. > > /*******vastly simplified**********/ > local j = 1 > gen k = 2 > gen l = 3 > > while `j' < 6 { > checkfoo `j' `k' `l' /* r(checked) returned equal to 1 when j = 2 or 3*/ > replace k = 4 if r(checked) == 1 > local j = `j' + 1 > } > /***********************************/ > I would like it to replace "k" on the 2nd and 3rd time through the loop but not at any other time. > > I would be happy if I could just do > /* psudocode */ > replace k = 4 if checkfoo `j' `k' `l' /* with checkfoo evaluating true or false */ > > Any and all suggestions for helping this classical programmer come up to speed would be greatly appreciated. I have the reverse problem, being totally unfamiliar with SAS. What do you mean by line? In what sense do you think -if- won't work? In general, if changes depend entirely on what is in each observation, in Stata's sense, you should not need to loop or to write programs. Nick n.j.cox@durham.ac.uk * * 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/

**References**:**st: Structure for making line by line changes?***From:*Daniel Sabath <sabathd@u.washington.edu>

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