Column statistics, such as mean for only selected rows.

[#1]

Hi. 

I qould like to have a jsl command to find either column mean, median, or sigma for the height column, but only where age is only 12 and 13.

I tried select rows, but I dont seem to get the correct result. If i use or not use the select rows, it still gives me the same numbers. 

Data Table( "table" ) << Select where( :age== { 12, 13  });
  Sigma = Col Std Dev( As Column( "age" ) );
median = Col Mean( As Column( "age" ) );

show (Sigma);
show (median);

dt << Clear Select;

I appreciate any help in this. 

[#2 · Accepted solution]

Here is the way I would handle this

Names Default To Here( 1 );
dt = Current Data Table();
sigma = Col Std Dev( If( :age == 12 | :age == 13, :Age, . ) );
Avg = Col Mean( If( :age == 12 | :age == 13, :Age, . ) );

[#3 · Accepted solution]

you asked for a JSL command - but maybe also interesting:

a very useful new feature in JMP 18: header statistics
they can be static - or (default setting) react on the row selection:

Via the preferences, the user can define which values are displayed.
It's amazing how many options are available.
I wish other platforms like Distribution, Tabulate, Summary, Summarize, and: Graph Builder  (!)
had such a large selection of items to choose from.

here is the wish:
Col N Categories - and all the others ... 

[what I miss the most: Col N Categories / N Unique in JSL and Graph Builder]