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| From | Steve Nakoneshny <scnakone@ucalgary.ca> |
| To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
| Subject | Re: st: creating a new variable |
| Date | Wed, 18 Jul 2012 05:40:45 -0600 |
Hi Amal, See -help egen-. A potential solution for you could look something like: bys gestwk: egen mbw = mean(bw) Steve Sent via carrier pigeon On 2012-07-18, at 4:34 AM, "Amal Khanolkar" <Amal.Khanolkar@ki.se> wrote: > Hi all, > > I have a very simple problem that I'm unable to find a simple solution for: > > Below is the data concerned: > > Gestational age in weeks: > > tab gestwk > > gestwk | Freq. Percent Cum. > ------------+----------------------------------- > 22 | 134 0.00 0.00 > 23 | 387 0.01 0.02 > 24 | 738 0.02 0.04 > 25 | 1,235 0.04 0.08 > 26 | 1,688 0.06 0.14 > 27 | 2,125 0.07 0.21 > 28 | 2,723 0.09 0.30 > 29 | 3,415 0.11 0.42 > 30 | 4,481 0.15 0.57 > 31 | 5,876 0.20 0.76 > 32 | 8,533 0.29 1.05 > 33 | 12,958 0.43 1.49 > 34 | 21,420 0.72 2.20 > 35 | 36,710 1.23 3.44 > 36 | 70,297 2.36 5.79 > 37 | 151,310 5.07 10.87 > 38 | 373,660 12.53 23.40 > 39 | 660,536 22.15 45.55 > 40 | 822,376 27.58 73.13 > 41 | 542,442 18.19 91.33 > 42 | 219,603 7.37 98.69 > 43 | 31,928 1.07 99.76 > 44 | 5,470 0.18 99.94 > 45 | 1,648 0.06 100.00 > ------------+----------------------------------- > Total | 2,981,693 100.00 > > > Mean birth weight of my study sample: > > . sum bw > > Variable | Obs Mean Std. Dev. Min Max > -------------+-------------------------------------------------------- > bw | 2980093 3502.431 575.7603 300 6780 > > sum bw if gestwk==26 > > Variable | Obs Mean Std. Dev. Min Max > -------------+-------------------------------------------------------- > bw | 1610 902.7248 189.5523 350 1970 > > . sum bw if gestwk==26 > > Variable | Obs Mean Std. Dev. Min Max > -------------+-------------------------------------------------------- > bw | 1610 902.7248 189.5523 350 1970 > > > Below, if I would like to look at the mean birth weight for a particular gestational week: > > . sum bw if gestwk==27 > > Variable | Obs Mean Std. Dev. Min Max > -------------+-------------------------------------------------------- > bw | 2024 1014.961 201.809 380 1920 > > . sum bw if gestwk==28 > > Variable | Obs Mean Std. Dev. Min Max > -------------+-------------------------------------------------------- > bw | 2613 1138.658 238.724 370 2000 > > . sum bw if gestwk==29 > > Variable | Obs Mean Std. Dev. Min Max > -------------+-------------------------------------------------------- > bw | 3316 1295.815 278.1803 370 2480 > > > What I would like to do is to create a single continuous variable that would give me the mean birth weight for each gestational week so that I don't have to look at it individually as above. I would like to ideally be able to use this variable in scatter plots. > > If I plot as follows: > > scatter twoway bw gestwk > > I of course don't get a single estimate for each gestational week, but instaed the entire range of birth weight for a particular week is plotted. > > Thanks! > > /Amal. > > * > * 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/ * * 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/