isDuplicated
Syntax
isDuplicated(X, [keep=FIRST])
Arguments
X is a vector or a tuple of vectors of same length.
keep can take the value of FIRST, LAST or NONE. It indicates how the system processes duplicate values. The default value is FIRST.
Details
Return a vector or a tuple of vectors of Boolean values. If an element has no duplicate values, it returns 0.
If keep=FIRST, the first duplicate value returns 0 while all other duplicate values return 1.
If keep=LAST, the last duplicate value returns 0 while all other duplicate values return 1.
If keep=NONE, all duplicate values return 1.
Examples
$ v = [1,3,1,-6,NULL,2,NULL,1]
$ isDuplicated(v,FIRST);
[0,0,1,0,0,0,1,1]
// 1 appears three time in v, the locations are the 0th, the 2nd and the 7th. Since keep = FIRST, the 0th result is set to false, and the 2nd and 7th results are set to true.
$ v = [1,3,1,-6,NULL,2,NULL,1]
$ isDuplicated(v,LAST);
[1,0,1,0,1,0,0,0]
// 1 appears three time in v, the locations are the the 0th, the 2nd and the 7th. Since keep = LAST, the 7th result is set to false, and the 0th and 2nd results are set to true.
$ v = [1,3,1,-6,NULL,2,NULL,1]
$ isDuplicated(v,NONE);
[1,0,1,0,1,0,1,1]
// 1 appears three time in v, the locations are the 0th, the 2nd and the 7th. Since keep = NONE, the 0th, the 2nd and the 7th result are all set to true.
To delete duplicate records from a table:
$ t=table(1 2 4 8 4 2 7 1 as id, 10 20 40 80 40 20 70 10 as val);
$ t;
id |
val |
|---|---|
1 |
10 |
2 |
20 |
4 |
40 |
8 |
80 |
4 |
40 |
2 |
20 |
7 |
70 |
1 |
10 |
$ select * from t where isDuplicated([id,val],FIRST)=false;
//Onlt keep the first duplicated record and delete the others.
id |
val |
|---|---|
1 |
10 |
2 |
20 |
4 |
40 |
8 |
80 |
7 |
70 |