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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: could someone pls explain me this |

Date |
Mon, 30 Apr 2012 19:33:12 +0100 |

You need to think of what the problem is to which this code is a solution. What is the value of a string variable corresponding to a value of a numeric variable? You can't say summarize <strvar> if <numvar> == # as -summarize- doesn't summarize string variables. So, you need to find out _where_ in the data it is true that <numvar>== # i.e. use a look-up technique. If a variable contains observation numbers, then r(min) and r(max) after -summarize- applied to that variable will also contain observation numbers. Nick On Mon, Apr 30, 2012 at 7:24 PM, tashi lama <ltashi32@hotmail.com> wrote: > thank you. I still have some clouds. > > 1.Why do we have to summarize the temp var? > > 2.Minimum such obs no r(min). Are we looking the minimum obs in the tempvar? Is it 3 in the following example? > > > > epcom noncom __000001 | > |------------------------------------------| > 1. | 18001 Acheres . | > 2. | 18002 Ainay-Le_Vieil . | > 3. | 18003 Les Aix -d'Angillion 3 | > 4. | 18004 Allogny . | > 5. | 18005 Allouis . | > > > > > 3. Could we have said instead of minimum or maximum no, non-missing obs no because there is only one obs in tempvar? > > ---------------------------------------- >> Date: Mon, 30 Apr 2012 18:37:56 +0100 >> Subject: Re: st: could someone pls explain me this >> From: njcoxstata@gmail.com >> To: statalist@hsphsun2.harvard.edu >> >> The code >> >> tempvar tv1 >> gene `tv1'=_n if depcom==18003 >> summ `tv1', meanonly >> local index=r(min) >> local mymacro=nomcom[`index'] >> drop `tv1' >> >> is a way of looking up the value of -nomcom- when -depcom- is 18003. >> The temporary variable contains observation numbers for which -depcom- >> is 18003. A certain way of finding such an observation if any exist is >> to find the minimum such observation number. The maximum would do fine >> as an alternative. The code could be shortened >> >> tempvar tv1 >> gene `tv1'=_n if depcom==18003 >> summ `tv1', meanonly >> local mymacro=nomcom[r(min)] >> drop `tv1' >> >> The main point of similar code is to automate value look-up. It's >> usually a long-winded way to proceed if you are working interactively. >> >> Nick >> >> On Mon, Apr 30, 2012 at 6:24 PM, tashi lama <ltashi32@hotmail.com> wrote: >> >> > I am doing sth similar to what I found in archive titiled "Re: st: save the value of a string variable into a macro". I am not sure if I followed the code although it looks relatively st. forward. >> > >> > >> > >> > Here is the dataset and goal >> > >> > +-----------------------------+ >> > | depcom nomcom | >> > |-----------------------------| >> > 1. | 18001 Acheres | >> > 2. | 18002 Ainay-le-Vieil | >> > 3. | 18003 Les Aix-d'Angillon | >> > 4. | 18004 Allogny | >> > 5. | 18005 Allouis | >> > +-----------------------------+ >> > >> > Where depcom is an id. I want to save a specific values of the variable "nomcom" into a variable, for example, I want to obtain : >> > . di "`mymacro'" >> > Archeres >> > >> > >> > >> > The code is >> > >> > >> > >> > tempvar tv1 >> > gene `tv1'=_n if depcom==18003 >> > summ `tv1', meanonly >> > local index=r(min) >> > local mymacro=nomcom[`index'] >> > drop `tv1' >> > >> > >> > >> > >> > I follow line 1 and 2. I am not sure why we need line 3. Line 4 established a macro which is used in line 5. But, I don't follow why the macro takes r(min) as expression. I would think the macro `index' should capture the value(the only value in fact) in tv1. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: could someone pls explain me this***From:*tashi lama <ltashi32@hotmail.com>

**References**:**st: could someone pls explain me this***From:*tashi lama <ltashi32@hotmail.com>

**Re: st: could someone pls explain me this***From:*Nick Cox <njcoxstata@gmail.com>

**RE: st: could someone pls explain me this***From:*tashi lama <ltashi32@hotmail.com>

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