topic Re: extend regression line through intercept in Discussions

extend regression line through intercept

dharding — Thu, 22 Feb 2018 21:32:11 GMT

Hi All,

there may be an easy way to do this but I haven't figured it out yet. I just want the regression line to pass through the y-axis at the intercept. So far, I can only get results like what I included in the attachment.

thanks for any help!

Re: extend regression line through intercept

XanGregg — Tue, 18 Oct 2016 20:24:22 GMT

If you're in Bivariate, just reset the X axis to include 0 before you add the Fit Line. The line will span all visible X values.

Re: extend regression line through intercept

dharding — Thu, 19 Sep 2013 18:41:32 GMT

Thanks so much! I knew it'd be a quick and easy one

Re: extend regression line through intercept

Byron_JMP — Thu, 19 Sep 2013 19:11:12 GMT

If you happen to forget to reset the axis before fitting the line...

Click the red triangle menu on the linear fit, and then select "set alpha level", 0.05 is the default so click that.

This will redraw the regression line, and it will also redraw the confidence intervals of the individual and fit too.

Re: extend regression line through intercept

tylerram93 — Fri, 18 Aug 2017 14:56:08 GMT

Do you know how to do this using the JMP script?

Re: extend regression line through intercept

txnelson — Fri, 18 Aug 2017 15:13:57 GMT

All you have to do to get the JMP script for this, is to generate the bivariate plot interactively, and then go to the red triangle in the output, and select "Save Script". It will give you your script for reproducing the chart.

Re: extend regression line through intercept

tylerram93 — Fri, 18 Aug 2017 15:47:04 GMT

Yes, but when I do that it doesn't work all the time. I have some plots I
generated that still don't work.

Tyler

Re: extend regression line through intercept

txnelson — Fri, 18 Aug 2017 19:13:50 GMT

Help==>Scripting Index==>Bivariate

will show you all JSL messages and statements that you may need to make the platform do what you want.

Re: extend regression line through intercept

tylerram93 — Thu, 22 Feb 2018 21:33:12 GMT

For most of them it works fine, but sometimes when I do both the Fit
Special and the Fit Line it doesn't go to zero, but the equation still has
an intercept of zero, is there a way to fix that?

Thanks,

Tyler

Re: extend regression line through intercept

mia_stephens — Thu, 22 Feb 2018 20:55:20 GMT

Xan, is there a way to do this for Fit Spline, either here or for the smoother in Graph Builder? I.e. extend the smoother through x=0?

Re: extend regression line through intercept

jules — Fri, 23 Feb 2018 16:43:52 GMT

Hi @mia_stephens,

It seems neither Graph Builder nor Fit Y by X will extend a smoother out of the box. There is a way to this, but it requires a few steps:

Launch Fit Y by X with your Y and X, and fit a spline of your choosing (Red Triangle > Flexible > Fit Spline).
Go to the Red Triangle for the smoothing fit > Save Predicteds. JMP will not just save the predicted Ys, but a prediction formula using the Spline Eval() function and a coefficient matrix.
Launch Graph > Graph Builder, add your predictor as the X, and the new saved formula column as the Y
Toggle the Formula graphing element
If you want to have the original points plotted, drag your original Y column to the drop zone to add a variable to Y, and then shift-click the Points element (or drag the points element to the plot).
You will be plotting points for both the formula column as well as the original Y; if you don't want this, expand the controls for the points and uncheck the box for the spline predictor under variables.

Now, whether or not this is a good idea of course depends on the data and how flexible that model is. In the example below this particular extrapolation returns a prediction of -29,714 lbs for someone 0 inches tall :)

I hope this helps!

@jules

Re: extend regression line through intercept

mia_stephens — Fri, 23 Feb 2018 17:59:06 GMT

Thanks Julian, will pass posting this along.

Mia