display mean number of observations per year

[tim bradshaw]

Hi there

Sorry for this very basic question. I want to display mean number of observation per year in my results window. My data are set up as follows. In this dummy example, the answer would be "8.333333"

clear
input float(year count)
2010 1
2010 1
2010 1
2010 1
2010 1
2011 1
2011 1
2011 1
2011 1
2011 1
2011 1
2011 1
2011 1
2012 1
2012 1
2012 1
2012 1
2012 1
2012 1
2013 1
2013 1
2013 1
2013 1
2013 1
2014 1
2014 1
2014 1
2014 1
2014 1
2014 1
2014 1
2014 1
2014 1
2014 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
2015 1
end

Any advice much appreciated. Thanks.

[Nick Cox]

. egen yrcount = total(count), by(year)

. egen tag = tag(year)

. su yrcount if tag 

    Variable |        Obs        Mean    Std. dev.       Min        Max
-------------+---------------------------------------------------------
     yrcount |          6    8.333333    4.226898          5         16

[Hemanshu Kumar]

With the community-contributed command distinct (from SSC), you can also do:

distinct year
dis "The mean no. of observations per year is `=r(N)/r(ndistinct)'."

which produces:

The mean no. of observations per year is 8.333333333333334.

[Nick Cox]

Good to hear recommendation of distinct, which is (please) better cited as coming from the Stata Journal (another extension will be published in early 2023 I hope).

The original paper at https://www.stata-journal.com/articl...article=dm0042 also explains ways of getting the number of distinct values without using distinct and just using official commands.

[tim bradshaw]

Great suggestions, thank you very much.