Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: st: RE: Calculating SD of a variable
From
lreine ycenna <[email protected]>
To
[email protected]
Subject
Re: st: RE: Calculating SD of a variable
Date
Wed, 19 Oct 2011 13:58:30 +0100
Hi, I forgot to respond to this, and now this problem's come back to
me. I udnerstand now that using -egen SD= sd(gdp), by(country year) -
generates missing observations, but how can I then calculate SD
according to both country and year? (i.e. no repeated sd for each year
or each country).
i.e. when I use egen SD= sd(gdp), by(country),
then I have the same SD for each country.
111 1979 USA 2.082018
111 1980 USA 2.082018
111 1981 USA 2.082018
111 1982 USA 2.082018
111 1983 USA 2.082018
111 1984 USA 2.082018
111 1985 USA 2.082018
111 1986 USA 2.082018
111 1987 USA 2.082018
111 1988 USA 2.082018
111 1989 USA 2.082018
when I use egen SD= sd(gdp), by(year),
then I have the same SD for each year.
111 1979 USA 6.972519
111 1980 USA 7.856638
111 1981 USA 8.209687
111 1982 USA 5.787104
111 1983 USA 6.855165
111 1984 USA 5.567018
111 1985 USA 5.427435
111 1986 USA 5.576608
111 1987 USA 5.678556
On 20 May 2011 12:05, Nick Cox <[email protected]> wrote:
> If you fire up -egen, sd()- using the option -by(countryno year)- then the combinations of country and year correspond to single observations. There can be no variability in a single observation, but what overrides that zero is that the SD calculation uses (n - 1) rather than n in the divisor, so n - 1 = 0 in that case and missing results are thus shown.
>
> Your problem remains vaguely stated, but note that SDs for countries would be
>
> egen SD = sd(gdp), by(countryno)
>
> and -- in general -- that the -by()- option defines groups within which SD is calculated.
>
> Nick
> [email protected]
>
> lreine ycenna
>
> I have a list of countries and their annual GDP growth rates. I need
> to calculate the standard deviations of the growth rate. But I seem to
> have done it wrong:
>
> Using the command egen sd = sd(gdp) gives me the same number for the
> entire column
>
> Using egen sd= sd (gdp), by(countryno year) gives me missing values.
>
> Am I missing something?
>
>
> My panel data looks like this:
>
> countryno year gdp
> 122 1995 1.448922432
> 122 1996 1.802327838
> 122 1997 1.939189289
> 122 1998 3.486108757
> 122 1999 3.057156394
> 122 2000 3.403232592
> 122 2001 0.706544087
> 122 2002 0.572674299
> 122 2003 0.806288363
> 122 2004 2.143516615
> 122 2005 2.0000
> 122 2006 3.021230987
> 124 1970 6.058892112
> 124 1971 3.1155209
> 124 1972 4.699826137
> 124 1973 6.212549621
> 124 1974 4.21133101
> 124 1975 -2.174872486
> 124 1976 5.612220928
> 124 1977 0.585991929
> 124 1978 2.844723097
> etc..
>
> *
> * 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/