# Calculate evol Y-1

Hello guys,

I’m facing a problem and I don’t succeed in finding a solution. I don’t know if this question was already asked (I swear I searched aha).

Each column corresponds to a month of a year. The first one is January 2000 and the last one is June 2019. I need to calculate the Y-1 evolution for each month and I don’t succeed even by using the math formula (multi columns) node. Do you think about a possible solution ? Last thing, the numbers correspond to the sum of all the rows for the same period.

Hi there @PatFr ,

can you explain what is y-1 evolution and how to calculate it? So you have same value in every column?

Br,
Ivan

I need to calculate the evolution for each month compared to the month of previous year. The table begins by January 2000 until June 2019. For example, in order to calculate evolution compared to Y-1 of January 2001, I need to do the following caluclation :

(Value of January 2001 - Value of January 2000) / Value of January 2000

And I need to do this caluclation for each month of each year

Hi there,

Oh. You mean Month to Month change if I’m correct. Well not sure there is a simple way to do it without coding. For example you can use Column Expressions node with multiple expressions like following:

(column(0) - column(12)) / column(12)

For each calculation you need one expression. Also I guess R, Python or Java are able to do this in some kind of a loop. Or maybe without loop. Don’t know Br,
Ivan

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