Gas (Petrol) Prices and how they fluctuate…

GeorgieAnne 

Do not panic!  I do not really expect you to adopt this style of programming Excel, but, in case you or some future reader of the thread are interested, I have taken the solution as bit further by introducing a Lambda function.

All that appears on the worksheet is

= DaysToReturnλ(regular)

= DaysToReturnλ(midGrade)

= DaysToReturnλ(premium)

= DaysToReturnλ(diesel)

in cells P2:S2.  I have created the chart for diesel prices as well because more seems to be going on there.

For completeness sake the formula, as shown within the advanced formula editor is

/*
"= DaysToReturnλ(grade)
returns period before a value returns to a prior local minumum value"
*/
DaysToReturnλ
= LAMBDA(grade, 
    LET(
        seq, SEQUENCE(COUNT(grade)),
        minimum, LocalMinsλ(grade),
        location, IF(minimum <> "", seq),
        MAP(
            location,
            minimum,
            LAMBDA(k, m, 
                IF(
                    k, 
                    LET(
                        valuesToSearch, DROP(grade, k),
                        nextOccurrence, XMATCH(m, valuesToSearch, -1),
                        IFERROR(nextOccurrence, "")
                    ),
                    ""
                )
            )
        )
    )
);

/*
"= LocalMinsλ(values)
retains local minimum values whist replacing other values by blank"
*/
LocalMinsλ
= LAMBDA(values, 
    LET(
        prior,  DROP(VSTACK(@(+values), values), -1),
        next,   DROP(VSTACK(values, 0), 1),
        minima, IF((values <= prior) * (values < next), values, ""),
        minima
    )
);

As you see, just as others work to make their Excel formulas more concise, I work to expand them, adding explanations and separating out areas of distinct functionality.