st: RE: RE: RE: on counting and fractions in stata

[Nick Cox <n.j.cox@durham.ac.uk>]

You can naturally also go 

gen byte above = series > 3.1 
su above, meanonly 
local mean = r(mean)
local total = r(N) 
local count = r(sum) 

and any extra conditions can be put on the -summarize-. 

In each case, "series > 3.1" would in careful code be "series > 3.1 & series < ." 

Nick 
n.j.cox@durham.ac.uk 


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: 27 October 2011 13:07
To: 'statalist@hsphsun2.harvard.edu'
Subject: st: RE: RE: on counting and fractions in stata

If you have other conditions, the pattern is 

count if series > 3.1 & <condition) 
local count = r(N)
count if <condition>
local total = r(N)
local fraction = `count'/`total' 

Nick 
n.j.cox@durham.ac.uk 

Nick Cox

. count if series > 3.1 
. local count = r(N) 
. local total = _N 
. di `count' 
. di `total' 
. di `count'/`total' 

-count- is a much-overlooked command. People seemingly don't find it or think it too simple. See e.g. 

SJ-7-1  pr0029  . . . . . . . . . . . . . . .  Speaking Stata: Making it count
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        Q1/07   SJ 7(1):117--130                                 (no commands)
        discusses count used with a loop over observations
        or variables

SJ-7-4  dm0033  . . . . . . Speaking Stata: Counting groups, especially panels
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        Q4/07   SJ 7(4):571--581                                 (no commands)
        discusses how to count panels through reduction commands
        or through tabulation commands and how to overcome
        problems that do not yield easily to these approaches

Nick 
n.j.cox@durham.ac.uk 

rado645-bg@yahoo.de


I face the following problem in Stata:

I have a series of daily observations on a given variable and I also have one estimate of this variable that serves as a threshold. 


I would like to estimate how many times this threshold is exceeded by comparing the value of this estimate with the available data on daily observations. Is it possible to estimate fractions in Stata in this particular way? 


Below is a simple example: 


series   estimate: 3.1
1.2
2.1
3.2
1.01

Given this data,I would like to get the following estimates (comments in brackets):

count:1 (threshold is exceeded only once)
fraction: 1/4=0.25 (one out of 4 cases)

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