This is a bit simpler and I think does what you want:
bysort citing nclass: gen byte unique = _n == _N
bys citing: replace unique = sum(unique)
by citing: keep if _n == _N
You should test this and maybe tweak it to deal with missing values, if
they exist in your data.
One point in your code: any command of this form "replace[_n]" will
generate an error code because Stata thinks your square brackets are
introducing weights and the syntax for -replace- does not permit
these. Also, you cannot use explicit indexing on a variable on the LHS of
a value assignment ("=") command.
Phil
At 11:41 PM 29/09/2003 -0500, you wrote:
Hi statalisters,
I have been working on a short program that doesn't seem to work, I think
I'm just missing a small mistake... I have a data file with three
columns: citing, cited, nclass. For every "citing", there are multiple
"cited", and for each "cited" there is a "nclass". The file is sorted by
citing, then nclass. I need a program to count the number of unique
"nclass" strings associated to each "citing".
As a simple example, given the following data file "data.dta":
citing cited nclass
100 20 12
100 22 15
100 23 15
101 32 14
101 33 15
101 34 15
101 40 17
I need the following output file:
citing numpatclass
100 2 [12 and 15 are unique, 15 is repeated]
101 3 [14, 15, 17 are unique, 15 is repeated]
I have decided to do it by creating an intermediate file which I will
later collapse(max):
citing cited nclass indexpatclass
100 20 12 1
100 22 15 2
100 23 15 2
101 32 14 1
101 33 15 2
101 34 15 2
101 40 17 3
"indexpatclass" indexes by 1 whenever a "citing" involves a new "nclass",
and resets to 1 whenever a new "citing" begins. So I have created a short
program. It sorts by "citing" and "nclass", then it uses a while-loop,
and then two if-loops. But there are two problems: (1) I am getting a
"weights not allowed" message when I try to run it. (2) I am also not
sure whether I am properly nesting my loops. Can anybody provide any
insight? Or alternatively, is there a much simpler way to do what I am
attempting?
Thanks, --Chihmao.
--------------------------------
# delimit cr
program define uniqpatclass
use c:\temp\data
generate indexpatclass=0
sort citing nclass
replace indexpatclass=1 in 1
generate id=_n
while id<_N {
if citing[_n]==citing[_n-1] {
if nclass[_n]==nclass[_n-1] {
replace indexpatclass[_n]=indexpatclass[_n-1]
id = `id' + 1
}
else {
replace indexpatclass[_n]=indexpatclass[_n-1]+1
id = `id' + 1
}
}
else {
replace indexpatclass[_n]=1}
id = `id' + 1
}
end
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Philip Ryan
Associate Professor,
Department of Public Health
Associate Dean (Information Technology)
Faculty of Health Sciences
University of Adelaide 5005
South Australia
tel 61 8 8303 3570
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http://www.public-health.adelaide.edu.au/
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