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Re: st: replacing with mean
From
Steven Samuels <[email protected]>
To
[email protected]
Subject
Re: st: replacing with mean
Date
Thu, 2 Dec 2010 09:40:30 -0500
Fabio Zona: Why do you want to impute the missing data? For all the
purposes that I can think of, mean replacement is an approach to
avoid. While it reproduces means, it distorts most other properties
of the observed and unknown complete data, including standard
deviations, correlations, and regression estimates. Consider one of
Stata's other imputation programs: -mi- in Stata 11; -mim- or -ice-
from SSC.
Steve
Steven J. Samuels
[email protected]
18 Cantine's Island
Saugerties NY 12477
USA
Voice: 845-246-0774
Fax: 206-202-4783
On Dec 2, 2010, at 3:42 AM, Nick Cox wrote:
No; it is not necessary as you could calculate the means in Mata. But
Michael's suggestion will typically be easier to work with.
-compress- usually gives extra memory painlessly.
Nick
[email protected]
Fabio Zona
...one more thing.... is it necessary to generate a new variable of
the mean? This consumes memory in stata..
Michael N. Mitchell
Will this do the trick?
egen missrev = mean(revenues), by(industry)
replace revenues = missrev if missing(revenues)
On 2010-12-01 10.31 PM, Fabio Zona wrote:
I have a set of industries, with a different number of firms in each
industry; per each firm I have a value, say it be Revenues
Industry Firm Revenues
A 1 100
A 2 150
A 3 missing1
A 4 120
B 5 80
B 6 130
B 7 missing2
..
I need to replace the missing value of Revenues with the mean of the
Revenues within the same industries (For example, missing1 for firm
3, needs to be replaced with the mean of the values 100, 150, 120,
that is, with the mean of the revenues of other firms 1, 2 and 4
which belong to the same industry to which firm 3 belongs).
I need to do this hundreds of time.
How can I do it easily?
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