RE: st: mean and SD by categories

["Dherani, Mukesh" <M.K.Dherani@liverpool.ac.uk>]

Thank you Nick and Federico. This code runs fine but ends up on one error message:

. estimation result m(all) not found

While I digest the code can you please let me know why?

BW,m


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Federico Belotti
Sent: 16 July 2013 14:09
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: mean and SD by categories

Ops. Sorry... I wrote the code too quickly

qui {
local lab
cap mat drop all mean sd up lo
forval a=1/2 {
	forval b=1/7 {
		forval c=1/5  { 
			sum bmi if sex==`a' & agegp==`b' & ses==`c'
			mat mean = nullmat(mean) \ r(mean)
			mat sd = nullmat(sd) \ r(sd)
			mat up = nullmat(up) \ r(mean)+(1.96*r(sd)/sqrt(r(N)))
			mat lo = nullmat(lo) \ r(mean)-(1.96*r(sd)/sqrt(r(N)))
			local lab `"`lab' "sex=`a' agegp=`b' ses=`c'""'
		}
	}
}
mat all = (mean,sd,lo,up)
mat rown all = `lab'
mat coln all = mean sd lb ub
noi estout m(all), varw(22) mlab(,none) }



On Jul 16, 2013, at 3:02 PM, Nick Cox wrote:

> You need to take square roots of the sample sizes in calculating 
> standard errors.
> Nick
> njcoxstata@gmail.com
> 
> 
> On 16 July 2013 13:56, Federico Belotti <f.belotti@gmail.com> wrote:
>> This could be a strategy to get a table using Ben Jann -estout- 
>> command
>> 
>> qui {
>> forval a=1/2 {
>>        forval b=1/7 {
>>                forval c=1/5  {
>>                        sum bmi if sex==`a' & agegp==`b' & ses==`c'
>>                        mat mean = nullmat(mean) \ r(mean)
>>                        mat sd = nullmat(sd) \ r(sd)
>>                        mat up = nullmat(up) \ r(mean)+(1.96*r(sd)/r(N))
>>                        mat lo = nullmat(lo) \ r(mean)-(1.96*r(sd)/r(N))
>>                        local lab `"`lab' "sex=`a' agegp=`b' ses=`c'""'
>>                }
>>        }
>> }
>> mat all = (mean,sd,lo,up)
>> mat rown all = `lab'
>> mat coln all = mean sd lb ub
>> noi estout m(all), varw(22) mlab(,none) }
>> 
>> Federico
>> 
>> On Jul 16, 2013, at 2:23 PM, Nick Cox wrote:
>> 
>>> There are various problems with your approach.
>>> 
>>> 1. The immediate problem is that you cycle over combinations of 
>>> categories creating local macros with names like mean111, sd111, and 
>>> so forth.
>>> 
>>> But a command like
>>> 
>>> display mean111
>>> 
>>> is understood by Stata to mean that you want to see a value of a 
>>> variable -mean111- or a scalar -mean111-, but you have no such 
>>> variable or scalar, hence the message you received.
>>> 
>>> To see the value of a local macro, you would need to do something 
>>> like
>>> 
>>> display `mean111'
>>> 
>>> 2. Adding +/- 1.96 SD to the mean is an attempt to get 95% 
>>> confidence intervals. But there are at least two problems here. 1.96 
>>> is an optimistic multiplier and a more accurate multiplier would be 
>>> based on the t-distribution. However, that's secondary compared with 
>>> using SDs when you should be using standard errors.
>>> 
>>> 3. A strategic difficulty here is that creating lots of local macros 
>>> first is not a good way to create graphs. In fact if you are a 
>>> novice in programming trying to program graphs from scratch is not advisable.
>>> In your case 70 cross-combinations seems likely to produce only a 
>>> very complicated graph. Much depends on whether each 
>>> cross-combination is well enough represented to show stable patterns.
>>> 
>>> -stripplot- from SSC may be of help. It has a -ci- option that means 
>>> that confidence intervals are shown for you.
>>> 
>>> Nick
>>> njcoxstata@gmail.com
>>> 
>>> 
>>> On 16 July 2013 12:43, Dherani, Mukesh <M.K.Dherani@liverpool.ac.uk> wrote:
>>>> Dear all,
>>>> I am very novice in programming.
>>>> I have a dataset with BMI by three categorical variables age (7 groups), sex (2 groups) and SES (5 groups).  I was to generate a line graph showing mean BMI with 95%CI by age , sex  and SES.  Below is my code to create local that I want to use in twoway line graph:
>>>> 
>>>> forval a=1/2 {
>>>> forval b=1/7 {
>>>> forval c=1/5  {
>>>> sum bmi if sex==`a' & agegp==`b' & ses==`c'
>>>> local mean`a'`b'`c'=r(mean)
>>>> local sd`a'`b'`c'=r(sd)
>>>> local up`a'`b'`c'=r(mean)+(1.96*r(sd)) local 
>>>> lo`a'`b'`c'=r(mean)-(1.96*r(sd)) di mean`a'`b'`c' sd`a'`b'`c' 
>>>> up`a'`b'`c' lo`a'`b'`c'
>>>> }
>>>> }
>>>> }
>>>> 
>>>> 
>>>> At the end of this command stata says mean111 was not found!
>>>> Secondly, I want graph to show me mean bmi (y axis) and age (x axis) for each ses for each sex separately. Should I carry this out in the loop or outside the loop?
>>>> 
>>>> Any help is highly appreciated.
>>>> 
>>>> BW,m
>>>> 
>>>> 
>>>> *
>>>> *   For searches and help try:
>>>> *   http://www.stata.com/help.cgi?search
>>>> *   http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/
>>> *   http://www.ats.ucla.edu/stat/stata/
>> 
>> --
>> Federico Belotti, PhD
>> Research Fellow
>> Centre for Economics and International Studies University of Rome Tor 
>> Vergata
>> tel/fax: +39 06 7259 5627
>> e-mail: federico.belotti@uniroma2.it
>> web: http://www.econometrics.it
>> 
>> 
>> *
>> *   For searches and help try:
>> *   http://www.stata.com/help.cgi?search
>> *   http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/

--
Federico Belotti, PhD
Research Fellow
Centre for Economics and International Studies University of Rome Tor Vergata
tel/fax: +39 06 7259 5627
e-mail: federico.belotti@uniroma2.it
web: http://www.econometrics.it


*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/