Transaction percentage total count in Stata - stata

Here is a sales transactions data set in Stata format. Each row is a sale of
a specific product
in a specific week
at a specific store
in a specific city
Some products were not sold at all stores in all weeks for a given city. For all products, I would like to calculate their market availability in that city in percentage points given certain week. For example, if product A was sold in week 1 in half of all the distinct stores in city (# of available stores changing from week to week), a new column would indicate market availability of 50% for all those observations (count). For different example, in the following sample data set for week 1, my desired variable market_availability would look like this (ignore the unit_sold column for now):
week store SKU city units_sold mkt_avail
1 200059 01182007 C 5 1
1 200060 01182007 C 4 1
1 200061 01182007 C 4 1
1 200060 01182090 C 6 0.66
1 200059 01182090 C 4 0.66
1 200061 01182888 C 1 0.33
2 200059 01182007 K 4 1
2 200060 01182007 K 1 1
2 200061 01182007 K 4 1
2 200059 01182090 K 8 0.66
2 200060 01182090 K 9 0.66
2 200061 01182888 K 4 0.33
This is a Stata table:
clear
set more off
input str5 week str8 store str30 SKU units_sold str1 city
1 200059 01182007 5 C
1 200059 01182090 4 C
1 200060 01182007 4 C
1 200060 01182090 6 C
1 200061 01182007 4 C
1 200061 01182888 1 C
2 200059 01182007 4 K
2 200060 01182007 1 K
2 200061 01182007 4 K
2 200059 01182090 8 K
2 200060 01182090 9 K
2 200061 01182888 4 K
end
The problem is that in this transactions data set, the same week store city SKU combinations can appear several times because of repeated purchases; but we don't want to consider repeated observations in the calculation of our shares because we already know that a specific item was available at that time.
I begin with tagging the unique observations by week and city
egen tag = tag(week city)
I also try
egen tag1 = tag(store SKU)
Now, should I try and match them up together?
Logically, I think I need first, to sum up distinct counts of city/ week/ store /SKU; then I need to calculate the number of stores in the city/week if SKU was ever sold for that combination. And then divide the first number by the second. Any thoughts?


Your strategy seems good. You can tag distinct (not "unique") observations just once in two ways and then calculate a fraction by dividing totals. This can all be done without any file choreography. The assumption here is that there are no observations recording zero sales. But if there are, then adding if units_sold to the tag() calculations should be sufficient to ignore them.
. clear
. set more off
. input str5 week str8 store str30 SKU units_sold str1 city
week store SKU units_s~d city
1. 1 200059 01182007 5 C
2. 1 200059 01182090 4 C
3. 1 200060 01182007 4 C
4. 1 200060 01182090 6 C
5. 1 200061 01182007 4 C
6. 1 200061 01182888 1 C
7. 2 200059 01182007 4 K
8. 2 200060 01182007 1 K
9. 2 200061 01182007 4 K
10. 2 200059 01182090 8 K
11. 2 200060 01182090 9 K
12. 2 200061 01182888 4 K
13. end
. egen tag = tag(city week store SKU)
. egen stores_selling_product = total(tag), by(city week SKU)
. egen tag2 = tag(city week store)
. egen stores_in_city = total(tag2), by(city week)
. gen fraction = stores_sell/stores_in
. sort week SKU store
. l week store SKU city stores* fraction , sepby(week)
+------------------------------------------------------------------+
| week store SKU city stores~t stores~y fraction |
|------------------------------------------------------------------|
1. | 1 200059 01182007 C 3 3 1 |
2. | 1 200060 01182007 C 3 3 1 |
3. | 1 200061 01182007 C 3 3 1 |
4. | 1 200059 01182090 C 2 3 .6666667 |
5. | 1 200060 01182090 C 2 3 .6666667 |
6. | 1 200061 01182888 C 1 3 .3333333 |
|------------------------------------------------------------------|
7. | 2 200059 01182007 K 3 3 1 |
8. | 2 200060 01182007 K 3 3 1 |
9. | 2 200061 01182007 K 3 3 1 |
10. | 2 200059 01182090 K 2 3 .6666667 |
11. | 2 200060 01182090 K 2 3 .6666667 |
12. | 2 200061 01182888 K 1 3 .3333333 |
+------------------------------------------------------------------+
On the terminology of distinct and unique in Stata context, and more importantly a review of technique in this territory, see this paper.


I think that this solution is not the best, but would work as your wish:
save original,replace // keeping your original dataset
collapse (count)has_sold=units_sold if units_sold>0, by(week store SKU city) // make binary flag for counting
replace has_sold=1 // force binary flag
save tmp,replace // preserving current status
bysort week store: keep if _n==1
egen numStoreWeekly = count(has_sold), by(week) // get total number of stores in week regardless city
drop SKU has_sold // dropping temporary variables
merge m:m week store city using tmp // adding numStoreWeekly to tmp.dta ("merge m:m" was used to assign same numStoreWeekly to same week/store/city combination)
egen numStoreSold = count(has_sold), by(week city SKU) // counting stores sold by week city SKU
gen mkt_avail = numStoreSold/numStoreWeekly
drop numStoreSold numStoreWeekly _merge has_sold // dropping temporary variables
merge m:m week store city SKU using original // merging back (adding mkt_avail to original.dta )
drop _merge
sort week city SKU store

Related

How to Count Distinct for SAS PROC SQL with Rolling Date Window of 5 years?

I want to count the distinct values of a variable grouped by MEMBER_ID and a rolling date range of 5 years. I have seen a similar post.
How to Count Distinct for SAS PROC SQL with Rolling Date Window?
When I change h2.DATE BETWEEN h.DATE - 180 AND h.DATE to h2.year BETWEEN h.year-5 AND h.year, should it give me the correct distinct count within the last 5 years? Thank you in advance.
data have;
input permno year Cand_ID$;
datalines;
1 2000 1
1 2001 2
1 2002 3
1 2003 1
1 2004 3
1 2005 1
2 2000 1
2 2001 3
2 2002 1
2 2003 2
2 2004 2
2 2005 2
2 2006 1
2 2007 1
3 2001 3
3 2002 3
3 2003 3
3 2004 1
3 2005 1
;
run;

Here's how you can do it with a data step. This assumes you have values for all years. If you do not, fill it in with zeros.
Keep a rolling list of the last 5 years by using the lag function. If we keep a rolling sorted array list of the last 5 years using lag, we can count the distinct values for each row to get a rolling 5-year count.
In other words, we're going to create and count a list that looks like this:
permno year id1 id2 id3 id4 id5
1 2000 . . . . 1
1 2001 . . . 1 2
1 2002 . . 1 2 3
1 2003 . 1 1 2 3
Code:
data want;
set have;
by permno year;
array lagid[4] $;
array id[5] $;
id1 = cand_id;
lagid1 = lag1(cand_id);
lagid2 = lag2(cand_id);
lagid3 = lag3(cand_id);
lagid4 = lag4(cand_id);
/* Reset the counter for the first group */
if(first.permno) then n = 0;
/* Count the number of rows within a group */
n+1;
/* Save the last 5 years by using the lag function,
but do not get lags from previous groups
*/
do i = 1 to 4;
if(i < n) then id[i+1] = lagid[i];
end;
/* Sort the array of IDs into ascending order */
call sortc(of id:);
/* Count the number of distinct IDs in the array. Do not count
missing values.
*/
n_distinct = 1;
do i = 2 to dim(id);
if(id[i] > id[i-1] AND NOT missing(id[i-1]) ) then n_distinct+1;
end;
drop lag: n i;
run;
Output (without id: dropped):
permno year Cand_ID id1 id2 id3 id4 id5 n_distinct
1 2000 1 . . . . 1 1
1 2001 2 . . . 1 2 2
1 2002 3 . . 1 2 3 3
1 2003 1 . 1 1 2 3 3
1 2004 3 1 1 2 3 3 3
1 2005 1 1 1 2 3 3 3

Combine overlapping categorical variables

I am trying to "combine" two categorical variables in Stata (say var1 and var2) into a new (also categorical) variable (say res).
The example below illustrates what I am trying to achieve:
var1 var2 res
1 1 A
1 2 A
2 1 A
3 3 B
4 2 A
5 4 D
What this example does is to combine all categories of var1 and var2 that "overlap".
Here, the pair var1 == 1 and var2 == 1 initially form a group (res== A). All other pairs containing var1 == 1 or var2 == 1 should belong to the same group (hence res== A in rows 2 and 3). Because in row 2 we have var2==2, any pair with containing var2==2 should belong to the same group. That's why in row 4 res== A.
Another way to look at this problem is using the following matrix:
| 1 2 3 4
-----------------------
1 | 1 1
2 | 1
3 | 1
4 | 1
5 | 1
Because the element [1,1] is not empty (or zero), all elements in row 1 and column 1 must belong to the same group. Because [1,2] is not empty, the same is true for row 1, column 2. And so on and so forth. It does not matter which row/column you decide to start from.
egen group alone doesn't cut it.
Any ideas?

Sounds like you want to further group var1 if the values of var2 are the same. If that's the case, then you can use a program I wrote called group_id that's available from SSC. To install it, type in Stata's Command window:
ssc install group_id
Here's an example of how you would use it:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(var1 var2) str1 res
1 1 "A"
1 2 "A"
2 1 "A"
3 3 "B"
4 2 "A"
5 4 "D"
end
gen long wanted = var1
group_id wanted, matchby(var2)
list, sep(0)
and the results:
. list, sep(0)
+----------------------------+
| var1 var2 res wanted |
|----------------------------|
1. | 1 1 A 1 |
2. | 1 2 A 1 |
3. | 2 1 A 1 |
4. | 3 3 B 3 |
5. | 4 2 A 1 |
6. | 5 4 D 5 |
+----------------------------+

Populating new variable using vlookup with multiple criteria in another variable

1) A new variable should be created for each unique observation listed in variable sku, which contains repeated values.
2) These newly created variables should be assigned the value of own product's price at the store/week level, as long as observations' sku value is in the same subcategory (subc) as the variable itself. For example, in eta2,3, observations in line 3, 4, and 5 have the same value because they all belong to the same subcategory as sku #3. [eta2,3 indicates sku 3, subc 2.]
3) x indicates that this is the original value for the product/subcategory that is currently being replicated.
4) If an observation doesn't belong to the same subcategory, it should reflect "0".
Orange is the given data. In green are the values from the steps 1, 2, and 3. White cells are step 4.
I am unable to offer a solution of my own, as searching for a
way to generate a variable using existing observations hasn't given me results.
I also understand that it must be a combination of forvalues, foreach, and levelsof commands?
clear
input units price sku week store subc
3 4.3 1 1 1 1
2 3 2 1 1 1
1 2.5 3 1 1 2
4 12 5 1 1 2
5 12 6 1 1 3
35 4.3 1 1 2 1
23 3 2 1 2 1
12 2.5 3 1 2 2
35 12 5 1 2 2
35 12 6 1 2 3
3 20 1 2 1 1
2 30 2 2 1 1
4 40 3 2 2 2
1 50 4 2 2 2
9 10 5 2 2 2
2 90 6 2 2 3
end
UPDATE
Based on Nick Cox' feedback, this is the final code that gives the result I have been looking for:
clear
input units price sku week store subc
35 4.3 1 1 1 1
23 3 2 1 1 1
12 2.5 3 1 1 2
10 1 4 1 1 2
35 12 5 1 1 2
35 12 6 1 1 3
35 5.3 1 2 1 1
23 4 2 2 1 1
12 3.5 3 2 1 2
10 2 4 2 1 2
35 13 5 2 1 2
35 13 6 2 1 3
end
egen joint = group(subc sku), label
bysort store week : gen freq = _N
su freq, meanonly
local jmax = r(max)
drop freq
tostring subc sku, replace
gen new = subc + "_"+sku
su joint, meanonly
forval j = 1/`r(max)'{
local J = new[`j']
gen eta`J' = .
}
sort subc week store sku
egen joint1 = group(subc week store), label
gen long id = _n
su joint1, meanonly
quietly forval i = 1/`r(max)' {
su id if joint1 == `i', meanonly
local jmin = r(min)
local jmax = r(max)
forval j = `jmin'/`jmax' {
local subc = subc[`j']
local sku = sku[`j']
replace eta`subc'_`sku' = price[`j'] in `jmin'/`jmax'
replace eta`subc'_`sku' = 0 in `j'/`j'
}
}

I worry on your behalf that in a dataset of any size what you ask for would mean many, many extra variables. I wonder on your behalf whether you need all of them any way for whatever you want to do with them.
That aside, this seems to be what you want. Naturally your column headers in your spreadsheet view aren't legal variable names. Disclosure: despite being the original author of levelsof I wouldn't prefer its use here.
clear
input units price sku week store subc
35 4.3 1 1 1 1
23 3 2 1 1 1
12 2.5 3 1 1 2
10 1 4 1 1 2
35 12 5 1 1 2
35 12 6 1 1 3
end
sort subc sku
* subc identifiers guaranteed to be integers 1 up
egen subc_id = group(subc), label
* observation numbers in a variable
gen long id = _n
* how many subc? loop over the range
su subc_id, meanonly
forval i = 1/`r(max)' {
* which subc is this one? look it up using -summarize-
* assuming that subc is numeric!
su subc if subc_id == `i', meanonly
local I = r(min)
* which observation numbers for this subc?
* given the prior sort, they are all contiguous
su id if subc_id == `i', meanonly
* for each observation in the subc, find out the sku and copy its price
* to all observations in that subc
forval j = `r(min)'/`r(max)' {
local J = sku[`j']
gen eta_`I'_`J' = cond(subc_id == `i', price[`j'], 0)
}
}
list subc eta*, sepby(subc)
+------------------------------------------------------------------+
| subc eta_1_1 eta_1_2 eta_2_3 eta_2_4 eta_2_5 eta_3_6 |
|------------------------------------------------------------------|
1. | 1 4.3 3 0 0 0 0 |
2. | 1 4.3 3 0 0 0 0 |
|------------------------------------------------------------------|
3. | 2 0 0 2.5 1 12 0 |
4. | 2 0 0 2.5 1 12 0 |
5. | 2 0 0 2.5 1 12 0 |
|------------------------------------------------------------------|
6. | 3 0 0 0 0 0 12 |
+------------------------------------------------------------------+
Notes:
N1. In your example, subc is numbered 1, 2, etc. My extra variable subc_id ensures that to be true even if in your real data the identifiers are not so clean.
N2. The expression
cond(subc_id == `i', price[`j'], 0)
could also be
(subc_id == `i') * price[`j']
N3. It seems possible that a different data structure would be much more efficient.
EDIT: Here is code and results for another data structure.
clear
input units price sku week store subc
35 4.3 1 1 1 1
23 3 2 1 1 1
12 2.5 3 1 1 2
10 1 4 1 1 2
35 12 5 1 1 2
35 12 6 1 1 3
end
sort subc sku
egen subc_id = group(subc), label
bysort subc : gen freq = _N
su freq, meanonly
local jmax = r(max)
drop freq
forval j = 1/`jmax' {
gen eta`j' = .
gen which`j' = .
}
gen long id = _n
su subc_id, meanonly
quietly forval i = 1/`r(max)' {
su id if subc_id == `i', meanonly
local jmin = r(min)
local jmax = r(max)
local k = 1
forval j = `jmin'/`jmax' {
replace which`k' = sku[`j'] in `jmin'/`jmax'
replace eta`k' = price[`j'] in `jmin'/`jmax'
local ++k
}
}
list subc sku *1 *2 *3 , sepby(subc)
+------------------------------------------------------------+
| subc sku eta1 which1 eta2 which2 eta3 which3 |
|------------------------------------------------------------|
1. | 1 1 4.3 1 3 2 . . |
2. | 1 2 4.3 1 3 2 . . |
|------------------------------------------------------------|
3. | 2 3 2.5 3 1 4 12 5 |
4. | 2 4 2.5 3 1 4 12 5 |
5. | 2 5 2.5 3 1 4 12 5 |
|------------------------------------------------------------|
6. | 3 6 12 6 . . . . |
+------------------------------------------------------------+

I am adding another answer that tackles combinations of subc and week. Previous discussion establishes that what you are trying to do would add an extra variable for every observation. This can't be a good idea! At best, you might just have many new variables, mostly zeros. At worst, you will run into Stata's limits.
Hence I won't support your endeavour to go further down the same road, but show how the second data structure I discuss in my previous answer can be produced. Indeed, you haven't indicated (a) why you want all these variables, which are just the existing data redistributed; (b) what your strategy is for dealing with them; (c) why rangestat (SSC) or some other program could not remove the need to create them in the first place.
clear
input units price sku week store subc
35 4.3 1 1 1 1
23 3 2 1 1 1
12 2.5 3 1 1 2
10 1 4 1 1 2
35 12 5 1 1 2
35 12 6 1 1 3
35 5.3 1 2 1 1
23 4 2 2 1 1
12 3.5 3 2 1 2
10 2 4 2 1 2
35 13 5 2 1 2
35 13 6 2 1 3
end
sort subc week sku
egen joint = group(subc week), label
bysort joint : gen freq = _N
su freq, meanonly
local jmax = r(max)
drop freq
forval j = 1/`jmax' {
gen eta`j' = .
gen which`j' = .
}
gen long id = _n
su joint, meanonly
quietly forval i = 1/`r(max)' {
su id if joint == `i', meanonly
local jmin = r(min)
local jmax = r(max)
local k = 1
forval j = `jmin'/`jmax' {
replace which`k' = sku[`j'] in `jmin'/`jmax'
replace eta`k' = price[`j'] in `jmin'/`jmax'
local ++k
}
}
list subc week sku *1 *2 *3 , sepby(subc week)
+-------------------------------------------------------------------+
| subc week sku eta1 which1 eta2 which2 eta3 which3 |
|-------------------------------------------------------------------|
1. | 1 1 1 4.3 1 3 2 . . |
2. | 1 1 2 4.3 1 3 2 . . |
|-------------------------------------------------------------------|
3. | 1 2 1 5.3 1 4 2 . . |
4. | 1 2 2 5.3 1 4 2 . . |
|-------------------------------------------------------------------|
5. | 2 1 3 2.5 3 1 4 12 5 |
6. | 2 1 4 2.5 3 1 4 12 5 |
7. | 2 1 5 2.5 3 1 4 12 5 |
|-------------------------------------------------------------------|
8. | 2 2 3 3.5 3 2 4 13 5 |
9. | 2 2 4 3.5 3 2 4 13 5 |
10. | 2 2 5 3.5 3 2 4 13 5 |
|-------------------------------------------------------------------|
11. | 3 1 6 12 6 . . . . |
|-------------------------------------------------------------------|
12. | 3 2 6 13 6 . . . . |
+-------------------------------------------------------------------+

clear
input units price sku week store subc
35 4.3 1 1 1 1
23 3 2 1 1 1
12 2.5 3 1 1 2
10 1 4 1 1 2
35 12 5 1 1 2
35 12 6 1 1 3
35 5.3 1 2 1 1
23 4 2 2 1 1
12 3.5 3 2 1 2
10 2 4 2 1 2
35 13 5 2 1 2
35 13 6 2 1 3
end
egen joint = group(subc sku), label
bysort store week : gen freq = _N
su freq, meanonly
local jmax = r(max)
drop freq
tostring subc sku, replace
gen new = subc + "_"+sku
su joint, meanonly
forval j = 1/`r(max)'{
local J = new[`j']
gen eta`J' = .
}
sort subc week store sku
egen joint1 = group(subc week store), label
gen long id = _n
su joint1, meanonly
quietly forval i = 1/`r(max)' {
su id if joint1 == `i', meanonly
local jmin = r(min)
local jmax = r(max)
forval j = `jmin'/`jmax' {
local subc = subc[`j']
local sku = sku[`j']
replace eta`subc'_`sku' = price[`j'] in `jmin'/`jmax'
replace eta`subc'_`sku' = 0 in `j'/`j'
}
}
list subc sku store week eta*, sepby(subc)
+---------------------------------------------------------------------------------+
| store week subc sku eta1_1 eta1_2 eta2_3 eta2_4 eta2_5 eta3_6 |
|---------------------------------------------------------------------------------|
1. | 1 1 1 2 4.3 0 . . . . |
2. | 1 1 1 1 0 3 . . . . |
|---------------------------------------------------------------------------------|
3. | 1 1 2 4 . . 2.5 0 12 . |
4. | 1 1 2 3 . . 0 1 12 . |
5. | 1 1 2 5 . . 2.5 1 0 . |
|---------------------------------------------------------------------------------|
6. | 1 1 3 6 . . . . . 0 |
|---------------------------------------------------------------------------------|
7. | 1 2 1 2 5.3 0 . . . . |
8. | 1 2 1 1 0 4 . . . . |
|---------------------------------------------------------------------------------|
9. | 1 2 2 3 . . 0 2 13 . |
10. | 1 2 2 5 . . 3.5 2 0 . |
11. | 1 2 2 4 . . 3.5 0 13 . |
|---------------------------------------------------------------------------------|
12. | 1 2 3 6 . . . . . 0 |
+---------------------------------------------------------------------------------+

Putting same income for same groupID

In my data, income was asked only to one person of the group.
householdID memberID income
1 1 4
2 2 .
1 2 .
2 3 .
2 1 3
But obviously, I need to fill them up like
householdID memberID income
1 1 4
2 2 3
1 2 4
2 3 3
2 1 3
How can I do this in Stata?

This is an elementary application of by:
bysort householdID (income) : replace income = income[1] if missing(income)
See for related material this FAQ
A more circumspect approach would check that at most one non-missing value has been supplied for each household:
bysort householdID (income) : gen OK = missing(income) | (income == income[1])
list if !OK

Stata: How to count the number of 'active' cases in a group when new case is opened?

I'm relatively new to Stata and am trying to count the number of active cases an employee has open over time in my dataset (see link below for example). I tried writing a loop using forvalues based on an example I found online, but keep getting
invalid syntax
For each EmpID I want to count the number of cases that employee had open when a new case was added to the queue. So if a case is added with an OpenDate of 03/15/2015 and the EmpID has two other cases open at the time, the code would assign a value of 2 to NumActiveWhenOpened field. A case is considered active if (1) its OpenDate is less then the new case's OpenDate & (2) its CloseDate is greater than the new case's OpenDate.
The link below provides an example. I'm trying to write a loop that creates the NumActiveWhenOpened column. Any help would be greatly appreciated. Thanks!
http://i.stack.imgur.com/z4iyR.jpg
EDIT
Here is the code that is not working. I'm sure there are several things wrong with it and I'm not sure how to store the count in the [NumActiveWhenOpen] field.
by EmpID: generate CaseNum = _n
egen group = group(EmpID)
su group, meanonly
gen NumActiveWhenOpen = 0
forvalues i = 1/ 'r(max)' {
forvalues x = 1/CaseNum if group == `i'{
count if OpenDate[_n] > OpenDate[_n-x] & CloseDate[_n-x] > OpenDate[_n]
}
}

This sounds like a problem discussed in http://www.stata-journal.com/article.html?article=dm0068 but let's try to be self-contained. I am not sure that I understand the definitions, but this may help.
I'll steal part of Roberto Ferrer's sandbox.
clear
set more off
input ///
caseid str15(open close) empid
1 "1/1/2010" "3/1/2010" 1
2 "2/5/2010" "" 1
3 "2/15/2010" "4/7/2010" 1
4 "3/5/2010" "" 1
5 "3/15/2010" "6/15/2010" 1
6 "3/24/2010" "3/24/2010" 1
1 "1/1/2010" "3/1/2010" 2
2 "2/5/2010" "" 2
3 "2/15/2010" "4/7/2010" 2
4 "3/5/2010" "" 2
5 "3/15/2010" "6/15/2010" 2
end
gen d1 = date(open, "MDY")
gen d2 = date(close, "MDY")
format %td d1 d2
drop open close
reshape long d, i(empid caseid) j(status)
replace status = -1 if status == 2
replace status = . if missing(d)
bysort empid (d) : gen nopen = sum(status)
bysort empid d : replace nopen = nopen[_N]
l
The idea is to reshape so that each pair of dates becomes two observations. Then if we code each opening by 1 and each closing by -1 the total number of active cases is their cumulative sum. That's all. Here are the results:
. l, sepby(empid)
+---------------------------------------------+
| empid caseid status d nopen |
|---------------------------------------------|
1. | 1 1 1 01jan2010 1 |
2. | 1 2 1 05feb2010 2 |
3. | 1 3 1 15feb2010 3 |
4. | 1 1 -1 01mar2010 2 |
5. | 1 4 1 05mar2010 3 |
6. | 1 5 1 15mar2010 4 |
7. | 1 6 1 24mar2010 4 |
8. | 1 6 -1 24mar2010 4 |
9. | 1 3 -1 07apr2010 3 |
10. | 1 5 -1 15jun2010 2 |
11. | 1 2 . . 2 |
12. | 1 4 . . 2 |
|---------------------------------------------|
13. | 2 1 1 01jan2010 1 |
14. | 2 2 1 05feb2010 2 |
15. | 2 3 1 15feb2010 3 |
16. | 2 1 -1 01mar2010 2 |
17. | 2 4 1 05mar2010 3 |
18. | 2 5 1 15mar2010 4 |
19. | 2 3 -1 07apr2010 3 |
20. | 2 5 -1 15jun2010 2 |
21. | 2 4 . . 2 |
22. | 2 2 . . 2 |
+---------------------------------------------+
The bottom line is no loops needed, but by: helps mightily. A detail useful here is that the cumulative sum function sum() ignores missings.

Try something along the lines of
clear
set more off
*----- example data -----
input ///
caseid str15(open close) empid numact
1 "1/1/2010" "3/1/2010" 1 0
2 "2/5/2010" "" 1 1
3 "2/15/2010" "4/7/2010" 1 2
4 "3/5/2010" "" 1 2
5 "3/15/2010" "6/15/2010" 1 3
6 "3/24/2010" "3/24/2010" 1 .
1 "1/1/2010" "3/1/2010" 2 0
2 "2/5/2010" "" 2 1
3 "2/15/2010" "4/7/2010" 2 2
4 "3/5/2010" "" 2 2
5 "3/15/2010" "6/15/2010" 2 3
end
gen opend = date(open, "MDY")
gen closed = date(close, "MDY")
format %td opend closed
drop open close
order empid
list, sepby(empid)
*----- what you want -----
gen numact2 = .
sort empid caseid
forvalues i = 1/`=_N' {
count if empid[`i'] == empid & /// a different count for each employee
opend[`i'] <= closed /// the date condition
in 1/`i' // no need to look at cases that have not yet occurred
replace numact2 = r(N) - 1 in `i'
}
list, sepby(empid)
This is resource intensive so if you have a large data set, it will take some time. The reason is it loops over observations checking conditions. See help stored results and help return for an explanation of r(N).
A good read is
Stata tip 51: Events in intervals, The Stata Journal, by Nicholas J. Cox.
Note how I provided an example data set within the code (see help input). That is how I recommend you do it for future questions. This will save other people's time and increase the probabilities of you getting an answer.