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From |
Eva Poen <eva.poen@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Perplexed by the SUM function |

Date |
Mon, 16 Mar 2009 22:17:40 +0000 |

Lena, the function sum() creates a _running sum_ over all observations of the expression within (). That is, sum will add up gh1 + gh2 + gh3 + gh4 + gh5 for observation 1, and then add gh1 + gh2 + gh3 + gh4 + gh5 for observation 2, and so on. See -help functions- to learn more about functions. You are looking for -egen-: egen gh_raw2 = rowtotal(gh1 gh2 gh3 gh4 gh5) Here is an example to show you what sum() does in -generate-: *** clear set obs 10 gen x = _n list gen runsum = sum(x) list *** Hope this helps, Eva 2009/3/16 Lena Cuisina <lenazoid@yahoo.com>: > > I have a very basic question. I’m adding up responses to 5 questions. Some of the questions have missing data. This is what I don’t want to do, because I don't want to lose the 23 observations: > > . gen gh_raw = gh1 + gh2 + gh3 + gh4 + gh5 > (23 missing values generated) > > . gen gh_avg = gh_raw/5 > (23 missing values generated) > > I want to use whatever data I’ve got from the other questions in calculating the sum -- ie, I’d like to great the missing as zero, not missing. So I tried the sum function: > > gen gh_raw1 = sum(gh1+gh2+gh3+gh4+gh5) > > gen gh_avg1 = gh_raw1/5 > > All 5 questions have the same 5-category ordinal response scale that’s coded 0, 25, 50, 75, 100. So the average of the 5 responses are within the 0 to 100 range. Unfortunately, the command I've written with the sum function gives me a set of average scores with a maximum of 18,800. It’s crazy. > > I have no idea what I’m doing wrong, because I’m pretty new to Stata. Sorry for such a basic question. > > Lena > * * 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/

**References**:**st: Perplexed by the SUM function***From:*Lena Cuisina <lenazoid@yahoo.com>

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