count(distinct val)

[#1]

Hello All,

Any function in  Jmp similar to count distinct in sql?

Examples:

How can I obtain the values of count distinct subjectsid in a new column in these tables with functions?

Thanks

TABLA 1               

subjectid             count distinct subjectid

a                                              5

b                                             5

c                                              5

a                                              5

b                                             5

d                                             5

e                                             5

TABLA 2               

subjectid             count distinct subjectid

a                                              3

b                                             3

c                                              3

a                                              3

[#2 · Accepted solution]

I can't readily think of a way to have a formula accomplish a COUNT DISTINCT.  However, you can get the value via a couple Table Summaries and a Table Join, which you can then code into JSL if you choose.

In Table A, Select Table --> Summary, Group By subjectid, select OK.  In the summary table, select Table --> Summary, Select subjectid, and select "N" under Statistics, select OK.  In the new table, delete the "N Rows" Column.  Go back to the first table, and select Table --> Join.  Then select to join with the last summary table with matching specification of Cartesian Join, then select OK.  The distinct count will show up in your original table.

If you were to script it:

dt = Current Data Table();

sumdt = dt << Summary( Group( :subjectid ), invisible );

sumsumdt = sumdt << Summary( Group, N( :subjectid ), invisible );

count_distinctdt = dt << Join(

     With( sumsumdt ),

     Cartesian Join

);

count_distinctdt << delete columns("N Rows");

column("N(subjectid)") << set name("count distinct subjectid");

sumsumdt << close window;

sumdt << close window;

close(dt,no save);

[#3]

A simple though inefficient formula is:

   Summation( i = 1, N Row(), :subjectid == :subjectid)

It takes advantage of the fact that true is 1 and false is 0, so summing up the comparisons gives a count.

Using the Table Summary method as TheChadd describes or using JSL will be faster if the table is really big.

[#4]

I found this aggregate function useful:

N Categories()

[#5]

Sadly, I can't find the N Categories() function in the Scripting Index.

Luckily I would be satisfied with any of the previous solutions.

// Open an example
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );

// Use the Tables > Summary command approach
dt << Summary(
	Group( :age ),
	Freq( "None" ),
	Weight( "None" )
);

// Use the Analyze > Tabulate approach
dt << Tabulate(
	Show Control Panel( 0 ),
	Add Table( Row Table( Grouping Columns( :age ) ) )
);

// Use the JSL Summarize() function approach
Summarize(
	group = By( :age ),
	n = Count()
);

[#6]

I was puzzled by @Beaux's response as well but I think he's referring to the N Categories summary statistic in Tables->Summary.

[#7]

Strange that that function is not available in the formula editor (statistical) or JSL... Maybe next version.

[#8]

As @Jeff_Perkinson says - really puzzling that there is a N categories functionality in Jmp - but that it's restricted to Tables/Summary ?!?

If other users are interested as well to have N Categories not just in the Tables/Summary Platform, but also via JSL ...
  - here is the wish:
new JSL function: Col N Categories 

[#9]

Tables/ Summary: 

Tabulate: 

Header Statistics:  

Graph Builder: NOPE

Col N Categories: NOPE

@Jeff_Perkinson , whom do we have to convince to get it implemented in JMP18.1?

[#10]

other posts with similar issues:

Add Counter for Unique Cases in Groups 

count unique 

Custom Function - how to reference the column 

Column reference in custom function 

count(distinct val) 
Formula for Number of Unique Categories in Column 

How Do I create a Column formula for N Categories?