×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Non-linear Trendlines

Non-linear Trendlines

Non-linear Trendlines

(OP)
In excel why is it that certain trendline options in Excel, such as logarithmic or exponential, don't appear when you have sufficient data to perform such an analysis?

corus

RE: Non-linear Trendlines

i do not quite understand your question, but there are exponential and logarithmic (among others) trendline features incorporated into excel.

simply select the series and right-click mouse.  choose add trendline and note the two tabs.

good luck!
-pmover

RE: Non-linear Trendlines

(OP)
thanks pmover but when you select the trendline only a certain number of the available options become available. A linear trendline always appears, as does a polynomial but the exponential, logarithmic, and power options are often greyed out and cannot be selected even though there are more than enough data points for a regression analysis to be performed. Why is that?

corus

RE: Non-linear Trendlines

There is something wrong in your installation, perhaps..

On mine, the only thing that grays out is moving average, and that's only if there are only two datapoints.

TTFN

RE: Non-linear Trendlines

negative values may kill logarthmics and so on. Given the rumoured flakiness of these trendlines I'd be inclined to roll my own anyway.

Cheers

Greg Locock

RE: Non-linear Trendlines

As GregLocock says, Excel can only calculate Trendlines when the range of x and y data is within allowable limits. Zero and negative values will make some options unavailable, but linear and polynomial fits should always be available.

RE: Non-linear Trendlines

I've noticed that the trendline in my Excel 2003 is smarter than the previous version I had.  It seems to make active only those trendlines that fit the data reasonable well.  For example, I generated y = log (x) data and put that onto a graph and the log trendline became active.  Some others were active too, but the log was not active on a previous data set I had.

Good luck,
Latexman

RE: Non-linear Trendlines

(OP)
Thanks, you're right, a negative number had slipped in unobtrusively.

corus

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close