how do i create two nested loops?

learning_JSL

Hi - I am attempting to write a script that follows this workflow:

 

1 - begin a loop on a certain starting datetime (e.g. Oct 1, 2021 11:00 AM).  I'll refer to this as row n.  Obtain value from col1[row n].

2 - go to next row, n+1. set col2 = col1 [n+1] - col1[n].   

3 - go to next row, n+2, set col2 = col1 [n+2] -  col1[n]

4 - go to next row, n+3, set col2 = col1[ n+3] - col1[n].   Continue to loop to through each subsequent row until datetime[n+k] =  datetime[n]  + 7 days.   (Note that k will vary depending on the time increment between rows as the loop proceeds; e.g. the time increases from one row to the next by 5 mins, 15 mins, 1 hr, etc, depending on the row in question.)

5 - Repeat steps 1 to 4 for each new week of data by using a new "start date" obtained in step 4.  Continue looping through another 7 days of data.

6 - Repeat step 5 until data table runs out of rows.   

 

The goal is to do computations on col1 data that compare a week's worth of rows to the first row of that week, and then to repeat this over and over for each subsequent week (week 2, week 3, week 4, etc) until all rows have been processed.    : )

 

vince_faller

Okay it sounds like you're saying 

 

Subtract the earliest flow point each day from each flow?  That's what you're trying to do?  I'm guessing because I don't think 13:15 AM is a thing.   

 

Names default to here(1);
dt = current data table(); // this assumes your table 
// I'm going to make a bunch of extra columns to kind of show you smaller steps

// we really want to be able to say, This is the first row of the day
// so let's make a date column
dt << New Column("Just Date", <<Formula(ShortDate(:DateTime)));
// now there are a bunch of ways to do this but if we just make sure it's sorted by date time.  
// We should be able to pick the first one easily enough. 

dt << Sort(By(:DateTime), Order( Ascending ), replace table);
// now we just want which row is the smallest per day
// for that we can colmin

// this is the column that will actually be the most useful.  
dt << New Column("smallest row for the day", formula(ColMin(Row(), :Just Date)));

// now we can just for make your difference column

dt << New Column("flow_difference", 
	formula(if(row() == :smallest row for the day, // if you don't care if it's missing don't need to do this
		.
	, // else
		:flow - :Flow[:smallest row for the day]
	))
);

you once you have the smallest row for the day, you only need to do the last new column however many times for as many columns as you want to compute the difference to.  

 

Hope I didn't overcomplicate things, cause I definitely didn't answer your original question of nested for loops.