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On 07/05/2017 23:48, Remy Gauthier wrote:

If you have one row per day of the year, you can find out easily where the row corresponding to "TODAY()-1" is located by finding out the number of days between Jan 1st of that year and "yesterday". This would be something like (you may need to adjust based on the heading of your column(s)):


The formula above calculates the number of days between yesterday last year and Jan 1st of last year. Now, you need to find in which column to add. Since you seem to have a heading providing the year, you can use the MATCH() function to locate the column:


This should give you the column where last year's data is located (I used a1 to z1, but any row reference will work).

To add the values, you now just need to use a combination of SUM() and OFFSET():


What that does:

OFFSET() allows you to create dynamic arrays for functions like SUM(). I used the anchor point $A$2 (I supposed your heading is in row 1), and told OFFSET to move from that reference 0 rows down and "MATCH(YEAR(TODAY()-1)-1;$a$1:$z$1;0)-1" columns to the right; then, from that new point, make an array that is "DAYS(YEAR(TODAY()-1)-1;MONTH(TODAY()-1);DAY(TODAY()-1);YEAR(TODAY()-1)-1;1;1)" rows high and 1 column wide. The resulting array is then used by SUM() to calculate the total rainfall.

This will probably need to be adjusted a bit to take into account the position of your column heading and to correctly find the row where to stop, but you should now have something to play with.

I hope this helps.

Rémy Gauthier.

Thank you for the in-depth reply! I will need to play with this and the functions you mention to get it right but hopefully I will come right. I will post my final formula here, for anyone else wanting to do something similar.

Le dimanche 07 mai 2017 à 21:55 +0200, Hylton Conacher (ZR1HPC) a écrit :

I have a spreadsheet I use to draw graphs and extract information about
the rainfall in my area for the last two years.

I need to create a formula that will count how many days it rained
between the start of the year, both last year and this year, so I can
compare the amount of rainfall that was received during that time frame.

The example below is a sample dataset that shows how much rainfall was
received in 2016 or 2017, on each of the four days

Month Day       2016    2017
Jan      1      0       15
Feb      29     1       0       
May      6      0       1
Sept     22     15      5

  From this we can determine that 16mm of rain fell in 2016 over 2 days.
Likewise we can determine that 21mm of rain fell in 2017 but over 3 days.

Today is the 7th of May 2017 and I would like a formula to work out how
many days the rainfall received between(and incl) 2016/01/01 and the day
before TODAY last year. The answer for 2016 is 1 i.e. it only rained
once between the dates specified, however the answer for 2017 is 16 as
it rained twice between TODAY-1 and 2017/1/1. I had thought of using
COUNTIF or DAYS or =COUNTIF(C2:SUM(TODAY()-1,">0")), however the problem
is that I do not have a single date column, but three.

This formula will allow me to create a graph showing how much rainfall
had fallen last year compared to this year between the beginning of the
year(01/01) and the day prior to Today.

I had thought of converting the first two columns into a single and
having the text name of the month with each successive line being a new
date in that month until the month changed, however I was unable to get
it to work i.e. automatically change month after 31 days in January to
read February 01.
As you can imagine I have 367 rows of data per year, mostly with 0 as a
value, however there are odd days it does rain.

Any comments, and if you want the original spreadsheet, just yell where
to put it i.e. Nabble etc.


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