suppose I have the following panel data (didn't include time var for simplicity)
clear
input id var
1 .
1 0
1 0
1 .
2 .
2 .
2 .
2 .
3 1
3 .
3 .
3 0
end
I would like to delete all groups that have all missing data in their group, that is, I want my data to be like:
id var
1 .
1 0
1 0
1 .
3 1
3 .
3 .
3 0
I tried doing a gen todrop = var[_N], but for some reason, for some groups it doesn't work. Any thoughts? I thought about sorting id var, then doing a cascade replace, but I'm sure there is a better way to do this.
In general, you can verify whether all observations hold the same value by checking first and last observations in each panel, after appropriate sorting. The same principle applies here. I'll use the missing() function:
clear
set more off
input id myvar
1 .
1 0
1 0
1 .
2 .
2 .
2 .
2 .
3 1
3 .
3 .
3 0
end
bysort id (myvar) : gen todrop = missing(myvar[1]) & missing(myvar[_N])
list, sepby(id)
In this case, just checking the first one also works. If it's missing, all others are.
See help by.
Roberto has provided a solution which is however case specific and might lead to wrong outcome.
In fact, suppose you have an observation as follows:
id myvar
2 .
2 1
2 .
Using Roberto's code, you would remove this group, while in the question you need to remove only if all observations are missing.
Therefore I suggest you use a different approach, as follows:
levels id, local(groups) // creates unique values for id (no need to egen if you don't really have to)
foreach iter of local groups {
mdesc myvar if id == "`iter'" // use mdesc and put double quotes if id is a string
drop if id == "`iter'" & r(percent) == 100 // r(percent) is stored after mdesc
}
Roberto's code definitely works. Also does below code. The only contribution is that the original order (sort) of observations is kept if you might want it.
egen todrop2 = min(missing(myvar)), by(id)
Related
I have a question about data set preparation. In a survey, the same people were asked about a number of different variables at two points of measurement. This resulted in a dataset in long format, i.e. information from each participant is stored in two rows. Each row represents the data of this person at the respective time of measurement (see example). Individuals have individual participation codes. The same participation code thus indicates that the data is from the same person.
code
time
risk_perception
DB6M
1
6
DB6M
2
4
TH4D
1
2
TH4D
2
3
Now I would like to create a new variable "risk_perception.complete", which shows me whether the information for each participant is complete. It could be that a person has not given any information at both measurement times or only at one of the two measurement times and therefore values are missing (NAs).In the new variable I would like to check and code this information for each person. If the person has one or more NAs, then a 0 should be coded there. If the person has no NAs, then there should be a 1 (see example).
code
time
risk_perception
risk_perception.complete
DB6M
1
6
1
DB6M
2
4
1
TH4D
1
2
1
TH4D
2
3
1
SU6H
1
NA
0
SU6H
2
3
0
VG9S
1
NA
0
VG9S
2
NA
0
Can anyone tell me the best way to program this?
Here is reproducible example:
data <- data.frame(
code = c("AH6M","AH6M","BD7M","BD7M","SH9L","SH9L"),
time = c(1,2,1,2,1,2),
risk = c(6,7,NA,3,NA,NA))
Thank you in advance and best regards!
I'd like to find any cases of a value (e.g., 0) in any cell in an SPSS database. What syntax would accomplish this?
(I came across a python script but don't have that option.)
It is still not very clear how you want to select those cases. But the below syntax will list in the output any cases which have ate least one "0" in any of the variables var1,var2 or var3. I am assuming CaseID is the case identifier variable.
TEMPORARY.
SELECT IF ANY(0,var1,var2,var3).
LIST CaseID var1 var2 var3.
You can use as many variables as you want in the ANY function, and also on the LIST command.
The following syntax will create a list of appearances of 0 within your data - In a separate file:
First creating some fake data to demonstrate on.
data list list/ID (a6) test1 to test6 (6f2).
begin data
ID_001 2 3 2 3 0 3
ID_002 3 4 0 4 3 4
ID_003 0 4 2 4 2 4
ID_004 7 0 1 2 8 3
ID_005 5 5 5 0 5 5
ID_006 4 5 4 5 4 0
end data.
dataset name origData.
Now to create the list:
dataset copy ForList.
dataset activate ForList. /* the list will be created from a copy of the data.
varstocases /make vals from test1 to test6/index testNum(vals).
select if vals=0.
You can use the list in the new file, or put it in the output window:
list ID testNum.
I have this kind of structure (ID and Event) :
ID Event X
A 0 0
A 0 0
A 1 1
A 0 1
B 0 0
B 1 1
B 0 1
B 1 2
B 0 2
B 0 2
B 1 3
And I would like to create X, but I can't use any loops as the data base is huge. I would appreciate any suggestion.
Edit: I tried some kinds of bysort ID and Event without luck: now I'm working with this approach:
gen Spell=Event
replace Spell=2 if Spell[_n-1]==1 & Spell[_n+1]==0 & ID[_n]==ID[_n-1]
but it's not going to work since I can't discriminate between the second or the third + event showing on the data base.
Solved
gen X=Event[_n]
replace X=X[_n]+X[_n-1] if _n>1 & ID[_n]==ID[_n-1]
Datasets like this need a time or other sequence variable. You should certainly create one if you don't have one:
sort ID, stable
by ID : gen t = _n
What you want is then just
bysort ID (t) : gen wanted = sum(event)
which is cleaner and clearer than what you have. In Stata
help sum()
search by
search spell
to see relevant help files and expository articles.
(You are aware of this approach, but as you don't show precisely what you tried, so we can't comment on what was wrong.)
I defined the macros below as levels of the variables id, var1 and var2:
levelsof id, local(id_lev) sep(,)
levelsof var1, local(var1_lev) sep(,)
levelsof var2, local(var2_lev) sep(,)
I'd like to be able to reference the level values stored in these macros by their index during foreach and forval loops. I'm learning how to use macros, so I'm not sure if this is possible.
When I try to access a single element of any of the above macros, every element of the macro is displayed. For example, if I display the first element of id_lev, every element is displayed as a single element (and, the last element is listed as an invalid name which I don't understand):
. di `id_lev'[1]
0524062407240824092601260226032604 invalid name
r(198);
Furthermore, if I attempt to refer to elements of any of the macros in a loop (examples of what I've tried given below), I receive the error that the third value of the list of levels is an invalid number.
foreach i of numlist 1/10 {
whatever `var1'[i] `var2'[i], gen(newvar)
}
forval i = 1/10 {
local var1_ `: word `i' of `var1''
local var2_ `: word `i' of `var2''
whatever `var1_' `var2_', gen(newvar)
}
Is it not possible to reference elements of a macro by its index?
Or am I referencing the index values incorrectly?
Update 1:
I've gotten everything to work (thank you), save for adapting the forval loop given in William's answer to my loops above in which I am trying to access the macros of two variables at the same index value.
Specifically, I want to call on the first, second, ..., last elements of var1 and var2 simultaneously so that I can use the elements in a loop to produce a new variable. How can I adapt the forval loop suggested by William to accomplish this?
Update 2:
I was able to adapt the code given by William below to create the functioning loop:
levelsof id, clean local(id_lev)
macro list _id_lev
local nid_lev : word count `id_lev'
levelsof var1, local(var1_lev)
macro list _var1_lev
local nvar1_lev : word count `var1_lev'
levelsof var2, local(var2_lev)
macro list _var2_lev
local nvar2_lev : word count `var2_lev'
forval i = 1/`nid_lev' {
local id : word `i' of `id_lev'
macro list _id
local v1 : word `i' of `var1_lev'
macro list _v1
local v2 : word `i' of `var2_lev'
macro list _v2
whatever `v1' `v2', gen(newvar)
}
You will benefit, as I mentioned in my closing remark on your previous question, from close study of section 18.3 of the Stata User's Guide PDF.
sysuse auto, clear
tab rep78, missing
levelsof rep78, missing local(replvl)
macro list _replvl
local numlvl : word count `replvl'
macro list _numlvl
forval i = 1/`numlvl' {
local level : word `i' of `replvl'
macro list _level
display `level'+1000
}
yields
. sysuse auto, clear
(1978 Automobile Data)
. tab rep78, missing
Repair |
Record 1978 | Freq. Percent Cum.
------------+-----------------------------------
1 | 2 2.70 2.70
2 | 8 10.81 13.51
3 | 30 40.54 54.05
4 | 18 24.32 78.38
5 | 11 14.86 93.24
. | 5 6.76 100.00
------------+-----------------------------------
Total | 74 100.00
. levelsof rep78, missing local(replvl)
1 2 3 4 5 .
. macro list _replvl
_replvl: 1 2 3 4 5 .
. local numlvl : word count `replvl'
. macro list _numlvl
_numlvl: 6
. forval i = 1/`numlvl' {
2. local level : word `i' of `replvl'
3. macro list _level
4. display `level'+1000
5. }
_level: 1
1001
_level: 2
1002
_level: 3
1003
_level: 4
1004
_level: 5
1005
_level: .
.
As an illustrative example, suppose this is your dataset:
cat sex age
1 1 13
1 0 14
1 1 .
2 1 23
2 1 45
2 1 15
If you want to create a table of frequencies between cat and sex, you tabulate these two variables and you get the following result:
tab cat sex
| sex
cat | 0 1 | Total
-----------+----------------------+----------
1 | 1 2 | 3
2 | 0 3 | 3
-----------+----------------------+----------
Total | 1 5 | 6
I am writing a Stata program where the three variables are involved, i.e. cat, sex and age. Getting the matrix of frequencies for the first two variables is just an intermediate step that I need for further computation.
cap program drop myexample
program def myexample, rclass byable(recall) sortpreserve
version 14
syntax varlist [aweight iweight fweight] [if] [in] [ , AGgregate ]
args var1 var2 var3
tempname F
marksample touse
set more off
if "`aggregate'" == "" {
local var1: word 1 of `varlist'
local var2: word 2 of `varlist'
local var3: word 3 of `varlist'
qui: tab `var1' `var2' [`weight' `exp'] if `touse', matcell(`F') label matcol(`var2')
mat list `F'
}
end
However, when I run:
myexample cat sex age
I get this result which is not what I expected:
__000001[2,2]
c1 c2
r1 1 1
r2 0 3
That is, given that age contains a missing value, even if it is not directly involved in the tabulation, the program ignores the missing value and does not take into account that observation. I need to get the result of the first tabulation. I have tried using summarize instead, but the same problem arises. When implemented inside the program, missing values are not counted.
You are complaining about behaviour which you built into your own program. The responsibility and the explanation are in your hands.
The effect of
marksample touse
followed by calling up a command with the qualifier
if `touse'
is to ignore missing values. marksample by default marks as "to use" those observations in which all variables specified have non-missing values; the other observations are marked as to be ignored. It also takes account of any if or in qualifiers and any zero weights.
It's also true, as #Noobie explains, that omitting missing values from a tabulation is default for tabulate in any case.
So, to get the result you want you'd need to modify your marksample call to
marksample touse, novarlist
and to call up tabulate with the missing option (if it's compulsory) or to allow users to specify a missing option which you then pass to tabulate.
You also ask about summarize. By design that command ignores missing values. I don't know what you would expect summarize to do about them. It could report a count of missing values. If you want that, several other commands will oblige, such as codebook or missings (Stata Journal). You can always include a report on missings in your program, such as using count to count the missings and display the result.
I understand your program to be very much work in progress, so won't comment on details you don't ask about.
This is caused by marksample. Rule 5 in help mark states
The marker variable is set to 0 in observations for which any of the
numeric variables in varlist contain a numeric missing value.
You should use the novarlist option. According to the help file,
novarlist is for use with marksample. It specifies that missing values
among variables in varlist not cause the marker variable to be set to 0.
if I understand well you want tab to include missing values? If so, you just have to ask for it
tab myvar1 myvar2, mi
from the documentation
missing : treat missing values like other values