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Re: st: RE: Survey and -catplot-


From   Harini Sarathy <harini.parth@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Survey and -catplot-
Date   Sat, 21 Jan 2012 11:57:21 -0500

Shaun,

Thanks for responding. I am using the same weight I used for the svy
analysis (I've sort of combined data from NHANES-III and the
continuous NHANES, so I created a new sampling weight).

While looking online for catplot help, I found someone suggesting that
I should use 'aweight' instead of 'pweight'. Stata also gives an error
if 'pweight' is used, so I guess 'aweight' is the correct usage for
weight.

I used the same sampling weight for aweight - frankly I don't know the
difference and what it means, and I just sort of aped the example.



Harini



On Sat, Jan 21, 2012 at 11:48 AM, Scholes, Shaun <s.scholes@ucl.ac.uk> wrote:
> Are you sure the weight specified in the catplot command was the same weight that was used in your svy commands? I have not analysed NHANES myself but I would expect to use a pweight rather than aweight?
> Can you check this using svydes (I'm assuming this is individual level NHANES data)?
> Best wishes
> Shaun
>
>
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
> Sent: 21 January 2012 15:58
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Survey and -catplot-
>
> Harini Sarathy <harini.parth@gmail.com> had difficulties sending this to the list. I will look at it shortly myself but anyone is naturally free to answer first.
>
> Nick
>
> I'm doing survey analysis with NHANES data from 1988-2008 and have been trying to use -catplot- (SSC) to show trends in abdominal obesity over the survey years (sddsrvyr) across age groups (agegrp):
>
> Abdominal obesity (abdobes) is a binary/discrete variable. (0 "Normal"
> 1 "Abdominal Obesity"
>
> sddsrvyr
> 1988-1996: 1
> 1999-2000: 2
> 2001-02    : 3
> 2003-04    : 4
> 2005-06:   : 5
> 2006-07    : 6
>
> For my analysis I created subpopulations for the age groups: sub_0812, sub_1317, sub_1840 (These subpopulations had complete data on variables of interest).
>
> The big picture: I have one binary variable (abdobes), two categorical variables (sub_0812/sub_1317/sub_1840 & sddsrvyr). I want to show the increasing trend in abdominal obesity over the survey years within each group - but I only want to show it for abdobes==1
>
> Proportions of obesity
>
> . svy: prop abdobes, sub(sub_0812) over(sddsrvyr) . svy: prop abdobes, sub(sub_1317) over(sddsrvyr) . svy: prop abdobes, sub(sub_1840) over(sddsrvyr)
>
> sub_0812: Abd Obese==1
>
> _sddsrvyr_1    .1099138
> _sddsrvyr_2    .1972264
> _sddsrvyr_3    .205952
> _sddsrvyr_4    .2562671
> _sddsrvyr_5    .2243748
> _sddsrvyr_6    .2589271
>
>
> sub_1318: Abd Obese==1
>
> _sddsrvyr_1    .1288447
> _sddsrvyr_2    .1717575
> _sddsrvyr_3    .1773453
> _sddsrvyr_4    .2003957
> _sddsrvyr_5    .1790184
> _sddsrvyr_6    .2129547
>
>
> sub_1840: Abdo Obese==1
>
> _sddsrvyr_1    .2576976
> _sddsrvyr_2    .3403194
> _sddsrvyr_3    .3599359
> _sddsrvyr_4    .3894223
> _sddsrvyr_5    .3934921
> _sddsrvyr_6     .394528
>
> For the purposes of a graph, I created a variable sub_all to represent all age-groups
>
> gen sub_all=0 if sub_0812==1
> replace sub_all=1 if sub_1317==1
> replace sub_all=2 if sub_1840==1
>
> The catplot command I used does not give me the graph I expected. Can you point out where I went wrong?
>
>
> catplot sddsrvyr sub_all [aweight=wtmeccombined] if abdobes==1,
> percent(sub_all) asyvars bar(1, bcolor(red)) bar(2, bcolor(midgreen)) bar(3, bcolor(sandb)) bar(4, bcolor(pink)) bar(5, bcolor(ebblue)) bar(6, bcolor(orange)) vertical title("Trends in Abdominal Obesity in NHANES population from 1988 to 2008 across age-groups",
> size(medsmall)) ytitle(%)
>
> According to the graph, I'm putting down approximations here
>
> sub_0812: Abd Obese==1
>
> _sddsrvyr_1    .18
> _sddsrvyr_2    .13
> _sddsrvyr_3    .165
> _sddsrvyr_4    .18
> _sddsrvyr_5    .17
> _sddsrvyr_6    .175
>
>
> sub_1318: Abd Obese==1
>
> _sddsrvyr_1    .22
> _sddsrvyr_2    .135
> _sddsrvyr_3    .1475
> _sddsrvyr_4    .17
> _sddsrvyr_5    .165
> _sddsrvyr_6    .175
>
>
> sub_1840: Abdo Obese==1
>
> _sddsrvyr_1    .25
> _sddsrvyr_2    .1475
> _sddsrvyr_3    .145
> _sddsrvyr_4    .15
> _sddsrvyr_5    .16
> _sddsrvyr_6    .15
>
> Given the values from the analysis, I'd expect an increasing trend in each age group. e.g. In age group 18-40, I expected it go from 25.7% to 39.4 %, whereas the graph shows something different.
>
> I know the problem lies in creating the variable "sub_all"and it does not seem to capture the information for the individual age groups.
> Does anyone have any ideas about what went wrong? And what is the way to correct it?
>
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