# trendline issues in an x-y plot

1. ## trendline issues in an x-y plot

i'm looking at ten years worth of data on a scatter plot. I ask for a sixth order polynomial to help make further decisions about the data. the equation is written on the plot, but is clearly not correct. does anyone know if the coefficients of the equation which generated the trendline are written somewhere accessible? does anyone know if one could define an output range to capture the trendline values? quite frustrated.

2. ## Re: trendline issues in an x-y plot

How did you determine that the trendline coefficients are not correct? My experience is that they are usually correct (they tend to default to too few significant figures, but are otherwise correct) for the regression as given.

If it is a simple matter of too few significant figures (very common for high order polynomials), simply format the trendline equation to display more digits (I like to use scientific notation like "0.00000000E+0", when I believe eight sig figs is sufficient).
Polynomials, like all of the other chart trendline equation options, are "linear" (or linearizable) and the regression can be performed directly in the spreadsheet using the LINEST() function (help file here https://support.office.com/en-us/art...a-fa7abf772b6d which includes an example for a 3rd order polynomial before the examples section).

3. ## Re: trendline issues in an x-y plot

Please update your user profile with the current version of Excel that you are using (visible on the splash screen when you run up Excel). Thanks.

I have closed the duplicate thread you started today - please continue here.

4. ## Re: trendline issues in an x-y plot

thanks ali. I realize I have some work to do on interaction. the only reason I tried again with the post today is the previous response regarding accessibility was not satisfactory. it was my mistake not to have followed up then.

5. ## Re: trendline issues in an x-y plot

Mr Shorty gave an answer based on the information you gave, which was not particularly detailed. Providing a sample workbook showing what you are trying to work with would help.

6. ## Re: trendline issues in an x-y plot

The LINEST() function is the easiest way to get trendline coefficients in the spreadsheet. If the Excel help file I linked to before is not helping you, maybe try reading through these other pages (found by putting "linest for polynomials" into my favorite internet search engine):
http://www.agcross.com/2014/01/excel...nts-trendline/
https://newtonexcelbach.com/2015/06/...-and-warnings/

There are other pages among the results as well.

7. ## Re: trendline issues in an x-y plot

thanks mrshorty. excellent references. sorry I was rude not to reply earlier. I've used linest() for linear analysis for some time now. I work alone, so have no one to chat with about these things. I see from your references that I may do precisely what I was hoping for all along. i'm excited to do better work more efficiently. thanks again

There are currently 1 users browsing this thread. (0 members and 1 guests)

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts

Search Engine Friendly URLs by vBSEO 3.6.0 RC 1