topic Re: Simple Question about Loops in Discussions

Simple Question about Loops

SrihariGopal — Sun, 13 Oct 2019 16:25:03 GMT

Hello,

I'm a longtime JMP user, but just recently started learning about scripts. I'm trying to learn the basics, and one of the key things I want to master is the use of for loops.

So I created a sample dataset with 4 columns:

1) PATIENTID: list of unique values for patient number
2) VALUE: Value of a patient rating at a particular timepoint
3) TIME: Timepoint at which patient rating was collected
4) PARAM: The patient rating is divided into 4 items and a total score

I wrote a script to iterate through all of the rows in this data table and to evaluate the values of two different variables (:TIME and :VALUE). If the condition is met, I'd like to add a character value to a row in a new column which is either Yes or No.

Here is the script that I wrote. JMP returns empty values for each of the rows in the new column:

Names Default To Here( 1 );
dt = current data table ();
tr = N Rows (dt);
dt << New Column ("TEST", "CHARACTER", 
For (i = 1, i <= tr, i++,
	If( 
		(:TIME == "BASELINE" & :VALUE > 3)
		,"YES"
		,"NO"
		)
	)
				)
	;

This is a simple script, and once I understand the mechanics, would like to add more conditions. But am stuck at this point because the script is not working properly.

I also tried writing this script using the For Each Row function, but still am having the same problem.

Any advice on what I'm doing wrong? Sorry if this is a simple answer, I looked through the documentation and can't seem to figure out what I'm doing wrong.

Re: Simple Question about Loops

SrihariGopal — Sun, 13 Oct 2019 16:30:35 GMT

Here is a similar script that I wrote to accomplish the same task, but instead using the For Each Row function. This doesn't work either.

Names Default To Here( 1 );
dt = current data table ();
dt << New Column ("TEST", "CHARACTER", 
For Each Row (dt, 
	If (
		(:TIME == "BASELINE" & :VALUE > 3)
		,"YES"
		,"NO"
		)
	)
				)
	;

Any help appreciated

Re: Simple Question about Loops

SrihariGopal — Sun, 13 Oct 2019 16:37:35 GMT

One more question:
The JSL documentation says that the for loops are incremented using the 3rd argument in the For function. I've seen this typically written as i++. I assume this means to increment i in place by 1. But what do I do if I want to increment by values less than 1? How do I write the argument?

The JSL documentation and the scripting index tool don't make any mention of how to do this.

Thanks

Re: Simple Question about Loops

MathStatChem — Sun, 13 Oct 2019 21:35:15 GMT

The task you are wanting to do can be accomplished in two ways:

a) use a Formula property for the column:

Names Default To Here( 1 );
dt = current data table ();
tr = N Rows (dt);
dt << New Column ("TEST", "CHARACTER", 
Formula(
	If( 
		(:TIME == "BASELINE" & :VALUE > 3)
		,"YES"
		,"NO"
		)
	)
				)
	;

b) iterate with a loop

Names Default To Here( 1 );
dt = current data table ();

dt << New Column ("TEST", "CHARACTER", Character, Nominal);
for(ii=1, ii<=N Rows(dt), ii++, 
:test[ii]=If( 
		(:TIME[ii] == "BASELINE" & :VALUE[ii] > 3)
		,"YES"
		,"NO"
		)
	);

you can also use For Each Row()

Names Default To Here( 1 );
dt = current data table ();

dt << New Column ("TEST", "CHARACTER", Character, Nominal);
for each row( 
:test=If( 
		(:TIME == "BASELINE" & :VALUE > 3)
		,"YES"
		,"NO"
		)
	);

Re: Simple Question about Loops

ms — Sun, 13 Oct 2019 21:49:47 GMT

It does not work because the loop is placed inside the New Column definition. Either create the column and fill its values in separate statements, or use a column formula.

Look at these three jsl examples that should give identical result:

Names Default To Here(1);
dt = Current Data Table();
tr = N Rows(dt);

//1. Fill values with a For() loop
dt << New Column("TEST", "CHARACTER");
For(i = 1, i <= tr, i++,
    :TEST[i] = If(:TIME[i] == "BASELINE" & :VALUE[i] > 3,
        "YES",
        "NO"
    )
);

//2. Fill with For Each Row()

dt << New Column("TEST2", "CHARACTER");
For Each Row(:TEST2 = If(:TIME == "BASELINE" & :VALUE > 3, "YES", "NO"));

//3. Use a column formula in TEST3
dt << New Column("TEST3",
    "CHARACTER",
    Formula(If(:TIME == "BASELINE" & :VALUE > 3, "YES", "NO"))
);

Re: Simple Question about Loops

ms — Sun, 13 Oct 2019 22:19:35 GMT

Loops are usually used for iterating through table rows or over items in a list, hence an increment by one is most common. However, the third argument must not be i++. It could be anything that makes sense.

A few examples:


For(i = 1, i <= 10, i = i + 0.1, Expr()); // Increment < 1 (100 iterations)

For(i = 10, i > 1, i--, Expr()); // Loop "backwards"

For(x = 2, x <= 10, x = 2, Expr()); // Eternal loop (better avoid these)