[GitHub] [systemds] BACtaki commented on pull request #1714: [SYSTEMDS-3254] Add new aliases for countDistinct built-in function

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BACtaki commented on PR #1714:
URL: https://github.com/apache/systemds/pull/1714#issuecomment-1306350347

   > Hi @BACtaki !
   > 
   > Thanks for the addition,
   > When i made the task i was trying to make the methods the same as in R, since much of the syntax is similar.
   > 
   > https://www.geeksforgeeks.org/unique-function-in-r/
   > 
   > Unfortunately it seems i was a bit quick in my decision, since unique != count distinct.
   > and what really is missing is the unique() function to return all unique elements in a matrix.
   > 
   > Sorry for the inconvenience.
   > 
   > Best regards
   > Sebastian.
   
   Thanks for clearing that up @Baunsgaard ! 
   
   > [..] what really is missing is the unique() function to return all unique elements in a matrix.
   
   I see a unique function in `builtins.java`:
   ```
   	UNIQUE("unique", true),
   ```
   
   In fact, there is an existing test for this function, which performs an equivalence check for the following:
   
   - `unique.dml`
   ```
   X = read($1);
   R = unique(X = X);
   write(R, $2);
   ```
   
   - `unique.R`
   ```
   args<-commandArgs(TRUE)
   options(digits=22)
   library("Matrix")
   
   X = as.matrix(readMM(paste(args[1], "X.mtx", sep="")));
   R = unique(X[order(X[,1]),]);
   writeMM(as(R, "CsparseMatrix"), paste(args[2], "R", sep=""));
   ```
   
   Is this the function you had in mind for the [JIRA](https://issues.apache.org/jira/browse/SYSTEMDS-3254) or was it something else? 


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