select or calculate values between rows

[Guest]

I've a column with values and I want another column with the calculation of
the difference between the current and the previous column, something like
this:
col 1 variation (from rows of column 1)
10 10 (row-row.previous => 10-0=10)
40 30 (row-row.previous => 40-10=30)
60 20 (row-row.previous => 60-40=20)

Is this possible with a simple expression?
What I (supose) need it's a way of select a row (previous or next) in a
Expression. Tks in advance

 

[John Vinson]

I've a column with values and I want another column with the calculation of
the difference between the current and the previous column, something like
this:
col 1 variation (from rows of column 1)
10 10 (row-row.previous => 10-0=10)
40 30 (row-row.previous => 40-10=30)
60 20 (row-row.previous => 60-40=20)

Is this possible with a simple expression?
What I (supose) need it's a way of select a row (previous or next) in a
Expression. Tks in advance

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John W. Vinson[MVP]