subset selection is empty, return error

[#1]

Hi all,

I am writing a script where I select a subset from a data table based on some criteria:

Example dt is my data table with column :Error_ID

I input: "dt_subset=dt<<select where (:Error_ID==0)<<subset(selected rows(1));" and I expect the dt_subset table to be filled by all the entries in the dt table where the column :Error_ID is 0.

Now let us say the dt data table has no Error_ID==0 rows, the dt_subset is empty.

I would have expected an dt_subset to be a new data table with the same columns as table dt but 0 rows, so that if I then check whether "If( !Empty(dt_subset)...)" I get a false and I do not continue doing work on the empty dt_subset table.

Instead I get an error if I try to check the if dt_subset is empty.

Basically what I want to do is be able to check if the selection is empty. Do you have a solution?

Thank you for your help!

[#2]

There are many different options You can check if selection is empty/no rows are found and then either use stop() or throw() to stop script execution (if it is suitable).

Names Default To Here(1);

dt = open("$SAMPLE_DATA/Big Class.jmp");

dt << Select Where(:age == 100);
// you can check for selections in dt table
If(N Items(dt << get selected rows) == 0,
	Show("No selections done");
);

dt_subset = dt << Subset(Selected Rows(1));
// you can check for dt_subset
If(Is Empty(dt_subset),
	Show("No subset table");
);

rows_to_subset = dt << Get Rows Where(:age == 100);
If(N Items(rows_to_subset) == 0,
	Show("No rows found");
);
// dt_subset = dt << Subset(rows(rows_to_subset));

[#3]

Hi Jarmo,

thank you for your reply. I had finally time to check this and I see that the following solution worked:

dt_subset = dt << Subset(Selected Rows(1));
// you can check for dt_subset
If(Is Empty(dt_subset),
	Show("No subset table");
);

The other two still returned errors: 

So I will use the second suggestion.

Best Regards, Valeria