topic Convert all radians columns to degrees in Discussions

Convert all radians columns to degrees

BHarris — Mon, 03 Feb 2025 23:55:15 GMT

I need a JSL loop that will search the column headers of a data table, and if the column header has "(rad)" in it, I'd like to multiply all of the values in that column by 180/pi, and then change "(rad)" to "(deg)" in the column header.

I have tried everything I can think of -- including chatGPT -- but so far no luck.

Re: Convert all radians columns to degrees

jthi — Tue, 04 Feb 2025 05:28:57 GMT

Get all columns using << Get Column Names
Set table to not update using << begin data update
Loop over them using For Each
Check if their name has (rad) in it using Contains / Starts With / Ends With
Use For Each Row to loop over it and change the values to degrees
1. I would hope there was better method for this, but I'm not sure if there really is unless you wish to create new columns and delete old as we shouldn't use << set each value which makes to extremely easy to do and read
2. Apply Formula in place (added in JMP18) might work but it is difficult to understand how to use it
3. Using matrix values is one good option but For Each Row will work always, always good idea to learn it
Use substitute and << Set Name to rename the column
let table update again using << end data update

Names Default To Here(1);

dt = New Table("Untitled",
	Add Rows(2),
	Compress File When Saved(1),
	New Column("Column 1", Numeric, "Continuous", Format("Best", 12), Set Values([., .])),
	New Column("a (rad)", Numeric, "Continuous", Format("Best", 12), Set Values([1, .]))
);

colnames = dt << Get Column Names(Continuos, "String");

dt << Begin Data Update();
For Each({colname}, colnames,
	If(Contains(colname, "(rad)"),
		For Each Row(dt, Column(dt, colname)[] = Column(dt, colname)[] * 180 / Pi());
		Column(dt, colname) << Set Name(Substitute(colname, "(rad)", "(deg)"));
	)
);
dt << End Data Update();

Write();

Re: Convert all radians columns to degrees

BHarris — Wed, 05 Feb 2025 07:01:56 GMT

Always impressive, thank you!

A few follow-on questions:

Why is "colname" in curly braces as the first argument of the for each loop?
I was trying to do something like "dt:colname[rowIdx] = dt:colname[rowIdx] * 180/Pi()" -- how would JMP interpreting this line and why is it wrong?
What does the "[]" do at the end of "Column(dt,colname)[]"? Is there a section of the documentation that discusses this construct?

Thank you again!

Re: Convert all radians columns to degrees

jthi — Wed, 05 Feb 2025 08:05:41 GMT

It is the syntax for For Each. Conditional and Logical Functions
Most likely JMP won't be able to interpret anything from that as it doesn't find colname column from your data table as colname just stores the value. I think you could use As Column instead of Column()[] and it might work
```
As Column(dt, colname) = As Column(dt, colname) * 180 / Pi()
```
[] is same as [Row()] and it is used to access current row when using Column(). Iterate on Rows in a Table