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Sum it up
Our first, real formula...
The sum formula will be our
first, real formula! This is one of the definitively most
widely used formulas.
The formula is built like this: =sum()
I guess the point of the formula is quite obvious, to "sum"
something... To be more specific, to sum any number of
numbers. With the sum formula you can enter the numbers to
sum or you can refer to cells in which the numbers are.
We’ll excamplify the latter now.
OK, let’s jump right into it! Make a list of numbers
like this:
Now we’ll try to sum these numbers, enter the formula
as following:
The "=" is very important, this tells
OpenOffice that this is a formula. The word
sum is important because it tells Calc
what to do with the numbers. The paranthesis with the cell
references are used to show Calc which numbers to do
something with.
Now, here’s a really cool trick; start entering the
forumula =sum( and nothing else! Now click
on the topmost cell that contains the numbers, and hold the
mouse button down while you drag down until you have marked
the entire area you want to evaluate. Enter
), the ending paranthesis.
What happened now? Calc actually entered the cell adresses
for you!
When you hit [Enter], your numbers will be
summed, like this:
Now, try changing the uppmost value. Do that by clicking
once on the cell, and start typing the number you want
entered:
Now you’ll see that Calc automatically updates the
sum to reflect the changes:
OK, delete the sum formula by selecting the cell, hit the
[Delete] button, and finally [Enter].
Re-enter the same formula as before:
When you hit [Enter], you get the sum to
the right of the area. This shows that you can place the
sum wherever you want, which you will experience sooner or
later is invaluable!
Now, try to enter a new number below the number in cell
A5, like below:
What happened with the sum formula? Nothing! Why? Because
we didn’t allow the formula to include any new
number. Go to the cell which contains the formula, press
[F2] to enter the edit mode. The cells
inclued in the formula will be bordered to show which area
is included in the formula. At the bottom right of the
formula you’ll see a handle, which you now should
click and hold, and drag down, so that you include also the
new number you entered:
Hit [Enter], and see that the formula now includes the last
number you entered.
Again, go to the the formula and hit [F2].
Change A6 to A1000:
Now, try to enter new numbers below the others, and see
what happens... You are now able to enter new numbers
without having to update the formula each time! Well, until
you’ve got 1000 numbers anyway... If you expect to
reach that many numbers, you can increas the number from
A1000 to A10000 e.g. But
try it as you’ve edited now:
NB: The dark marking is done to examplify new numbers.