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Calculating a Difference
Your spreadsheet holds a column of dates, weekdays, and a column of weights.
We would like to see the difference between our weight on a day-to-day basis.
Make a fresh column heading "Difference" at the top of the next available column.
Then drop down two cells.
We will key in a simple formula that calculates the difference between two nearby cells.
Your cell pointer is resting in the empty cell where you would like to see displayed the difference in weight from one day to the next.
Which days?
At this stage I would like you to say out loud "The difference between", and then point, with your finger tip, touching the screen, to the very first cell in which you keyed in a weight value.
In my example above it is the cell immediately below the "Weight" label, and the cell holds the value "161".
As you point with your finger to that cell, say "This".
Then point to the cell immediately below (in my example "162") and say "and this".
"The difference between this (points) and this (points)".
If we were explaining things to another human, that's what we would do, to state our intentions.
We do the same thing with the spreadsheet, except that the spreadsheet doesn't (yet) take voice or touch commands, so we will use the arrow keys.
Your cell pointer is still resting in the empty cell where you would like to see displayed the difference in weight from one day to the next.
Start a formula by tapping the equals key (near the top-right corner of the main block of keys on your keyboard), and then use the up- and left-arrow keys to point to that first data cell ("161" in my example)
Mid-construction your spreadsheet will look like this:
Now tap the minus (or "hyphen") key; it lies immediately to the left of the equals key.
Now tap the left-arrow key, just once, to point to your second data cell ("162")
Finally, tap the Enter key.
Finally, use the Fill-Down technique to propagate this newly formatted formula down to the last row of your data.
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Friday, February 05, 2010 5:47 AM
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