How does the Trend value work in my weight log?

I've been using this site for over a year and I still don't entirely understand the green "trend" line on my weight chart.

For the last four days my weight has been decreasing and the trend was also decreasing. Then today my weight decreased by twice the amount it has on any of the previous four days, but suddenly the trend value shot up.

It frustrates me not to know the mathematics behind this trend value. If anyone knows what it is, please let me know. I can handle it.

(PS to the developers, I tried to wrap the word Trend in double quotes in this title, and the app cut out the first double quote and all following characters.)

I would like to know this too. Ive ignored it since I started logging my weight on here because I just dont understand it!

When I think I have it figured out I enter a new weight and my theory goes out the window.

I'm going to take this as a sign that nobody really knows how this thing works, and that the person who wrote the algorithm for it doesn't look in on these forums.

I was just about to post the same question! I would like to know also. I weigh 183 and the trend is 188? Maby it's what you would weigh later in the day from eating or drinking.    

On your weight log page, you will see a small question mark on the right side.  That's the FAQ and help key.  If you click it it give the explanation of the trend line.

It is simply a running average, based on recent log entries.  It smooths out the small variations and shows the trend of your progress.  As long as the trend line angles down, you are fine, even if you have a gain for the day or week.  If it levels off, that shows a plateau.  If it angles up, it shows that you are gaining weight.

Hope this helps.

I thought it was something like that, but I lost weight four days in a row, with the fourth day being the biggest loss. The trend was also slowly dropping, but on the fourth day, the day I lost the most weight, suddenly the trend jumped UP to be higher than it was at the start of the four day period!

Why would the trend shoot up on the fourth consecutive day of weight loss?

As clairelaine said, it's a running average.  And you're on the right track as far as weight loss, as long as you aren't running into plateaus or getting an angle up.  Overall, the trend is more reliable than your daily weights, though the daily weights can be pretty encouraging along your weight loss journey.  It takes longer for the trend line, or average, to note a weight loss/gain.  ;)

The trend used for the CC weight log is merely the average of the most recent 10 data points given.  If you log a weight every day, this is going to be the last 10 days, including today.  (I'm a daily weigher.)

I suspected this and verified it by copying the data into a spreadsheet.  In a new column, I used the =Average() function.  I had to keep altering the cells to be included until I got to 10.  Then I could just do a "Fill Down" and all of my numbers matched the ones given by the CC trend.  I checked that the numbers actually matched with an =If() function that compared my values with the CC trend values, so I know this is correct.  I have more than 500 data points, for which everything matched. 

I just wanted to share this with all of the other math geeks out there.  And I wanted to let the non-math-geeks know that there was absolutely some rhyme and reason to this...  :)

Bottom Line: The CC trend on the weight log is the average of the last 10 weights entered.  Anything weirdness that you are noting is purely mathematics, not a quirkiness of this site.

If your trend value shot up, I imagine what happened is that a lower weight was suddenly not being included in the last 10 weights.  I'm guessing that there was a small gain recently (immediately prior to the 4 consecutive days with losses), followed by a gradual loss but not as quickly as the gain.  (I've seen this in my own trends values...)

The gain could have been water weight, since as we know 16oz of water is equal to about a pound.  If I weigh at different times during the day, my weight will go up as much as 3 pounds, so I always weigh first thing in the morning with an empty bladder (to compare apples with apples).

Thank you panda for your excel testing.  It saved me the time.

This doesn't seem like a good "trend" to use though.  If you consistently lose weight and never have an increase your actual weights continually diverges from the trend until you get enough entries, but then it is still significantly higher than the entered weights.  i.e. I only weight myself about once a week so since I restarted my exercise program all weights are lower than the earlier one, with one exception and the trend line is always above my actual line with a increasing variance.  A better trend would be a rate or slope average so you can project how long it will take to lose weight if you keep up your program, or if you begin slipping.  The estimated goal time also seems to be tied to the trend rather than actual entries.

I hope CC reads this thread and notes the issues people have with the trend line.  It is not intuitive for most people and only seems to work well for frequent or daily weighers.