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Re: Extend linear regression line in JMP version 13

RobRobeyns

New Contributor

Joined:

Feb 2, 2017

Hi,

 

I have a question regarding the Fit Line functionality in version 13.

In version 10, I was able to make graphs with a linear regression line that extended beyond the data points (see figure). However in version 13 the linear regression line stops at the last data point. Is there a setting in version 13 to achieve the extension of the linear regression beyond the last data point?

 

Thanks!

1 ACCEPTED SOLUTION

Accepted Solutions
julian

Staff

Joined:

Jun 25, 2014

Solution

I agree with Jim's concerns about extrapolating beyond the range of data observed. However, if you wish to do this you can add in a new row to the table with a value beyond the range of data for just your X variable, and JMP will then extend the line to that point. Since there is no Y value associated with that row this will not change the regression results. 

 

Extrapolate.gif

 

 

 

 

7 REPLIES
txnelson

Super User

Joined:

Jun 22, 2012

You can use either the annotation tools, or in JSL use the Add Graphics capability to add to the fit line, however, since it is a regression, which is based upon the parameters within the data, and not a forcasting tool, having the fit line project beyond the known data points would be statictically improper.  So what you are seeing is a correction of an error in JMP 10.

Jim
julian

Staff

Joined:

Jun 25, 2014

Solution

I agree with Jim's concerns about extrapolating beyond the range of data observed. However, if you wish to do this you can add in a new row to the table with a value beyond the range of data for just your X variable, and JMP will then extend the line to that point. Since there is no Y value associated with that row this will not change the regression results. 

 

Extrapolate.gif

 

 

 

 

RobRobeyns

New Contributor

Joined:

Feb 2, 2017

Great! Thanks for the feedback!

cfranklin333

Community Trekker

Joined:

Feb 19, 2016

Adding a 0 on x didn't work.  Had to use Annotation tools with fit where intercept is forced to zero where it is impossible to have any other intercept value other than (0,0).

Highlighted
Dan_Obermiller

Joined:

Apr 3, 2013

There are, obviously, times where you want to force the intercept to 0, but a caution: this changes the interpretation of many of the regression statistics that you are looking at. Essentially, by forcing the intercept to be 0, you are saying that the mean is 0 (think of centered/scaled data). This can be especially problematic if you are extrapolating beyond the range of your data.

 

Another simple way to think of this: think of a plot of height versus weight. You can fit a line to that data. Should that line be forced to go through the (0,0) point? If you have no height, you would not have a weight so it makes sense. However, the linear relationship likely would not hold from the lowest height datapoint to 0. Forcing it to be linear across the entire range can cause problems.

cfranklin333

Community Trekker

Joined:

Feb 19, 2016

Also need to extrapolate for stability / shelf-life extension based on 95% CI of trend. Unable to get Degradation to provide similar to existing visual plots.
markbailey

Staff

Joined:

Jun 23, 2011

You can use Bivariate > Fit Special command to select a No Intercept trend analysis.