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Re: st: mean and SD by categories
From
Federico Belotti <[email protected]>
To
[email protected]
Subject
Re: st: mean and SD by categories
Date
Tue, 16 Jul 2013 15:08:31 +0200
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
> [email protected]
>
>
> On 16 July 2013 13:56, Federico Belotti <[email protected]> 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
>>> [email protected]
>>>
>>>
>>> On 16 July 2013 12:43, Dherani, Mukesh <[email protected]> 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: [email protected]
>> 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: [email protected]
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/