How do you mark unique occurrences in a pattern given that value are unique when occurring simultaneously and not when they come separately? [closed] - sql

Question

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 7 years ago.
Improve this question
Suppose my data looks like this
student article.bought
1 A pen
2 B pencil
3 V book
4 A pen
5 A inkbottle
6 B pen
7 B pencil
8 B pencil
9 V book
10 Z marker
11 A inkbottle
12 V book
13 V pen
14 V book
I need unique occurrences of articles probably in a different column like this
student article.bought Occurences
1 A pen 1
2 B pencil 1
3 V book 1
4 A pen 1 # as A is taking a pen again
5 A inkbottle 2 # 'A' changed from pen to ink bottle
6 B pen 2
7 B pencil 3 # though B took pencil before, this is different as he took a pen in between
8 B pencil 3
9 V book 1
10 Z marker 1
11 A inkbottle 2
12 V book 1
13 V pen 2
14 V book 3

Answer 1

In R, we can find changes in a student's selection by finding the difference, diff, of each subsequent value. When we take the cumulative sum, cumsum, of that logical index we get a running count of occurrences.
In the second line we coerce the factor variable article.bought to numeric and run the function from the first line using ave to group the function f by student.
f <- function(x) cumsum(c(F, diff(x) != 0)) + 1
df$Occurences <- with(df, ave(as.numeric(article.bought), student, FUN=f))
df
# student article.bought Occurences
# 1 A pen 1
# 2 B pencil 1
# 3 V book 1
# 4 A pen 1
# 5 A inkbottle 2
# 6 B pen 2
# 7 B pencil 3
# 8 B pencil 3
# 9 V book 1
# 10 Z marker 1
# 11 A inkbottle 2
# 12 V book 1
# 13 V pen 2
# 14 V book 3

Answer 2

create additional column [Original Sort Order] and enumerate from 1
to ...
sort table by student / orig sort order
enter =IF(A2=A1,IF(B2=B1,D1,D1+1),1) in D2 and copy down
convert column D to values (copy, paste as ... Values)
restore original sort order
If this is more than a one-off, use the same tactic to create a VBA script

Answer 3

A shot with SAS:
data try00;
length student article $20;
infile datalines dlm=' ';
input student $ article $;
datalines;
A pen
B pencil
V book
A pen
A inkbottle
B pen
B pencil
B pencil
V book
Z marker
A inkbottle
V book
V pen
V book
;
data try01;
set try00;
pos=_n_;
run;
proc sort data=try01 out=try02; by student pos article; run;
proc sort data=try02 out=stud(keep=student) nodupkey; by student; run;
data shell;
length occurrence 8.;
set try02;
if _n_>0 then delete;
run;
%macro loopstudent();
data _null_; set stud end=eof; if eof then call symput("nstu",_n_); run;
%do i=1 %to &nstu;
data _null_; set stud; if _n_=&i then call symput("stud&i",student); run;
data thisstu;
set try02;
where student="&&stud&i";
dummyart=lag(article);
retain occurrence 0;
if dummyart ne article then occurrence=occurrence+1;
else occurrence=occurrence;
drop dummyart;
run;
proc append base=shell data=thisstu; run;
%end;
proc sort data=shell out=final; by pos; run;
%mend loopstudent; %loopstudent();
dataset "final" has the result.