Is there a possibility to apply a fit line on each data segment separately, so a line each on large, medium and small. With data filter I could only apply a fit if I present the graph separately. But I don't want that, I want all the bars and the fit line in the same grid. I hope someone can help.
Are you looking for something like this?
If so, you can use the Cols > Utilities > Labels to Codes tool to assign numeric values to each category. After that, change the X axis variable to continuous, and the line span the "categories."
I'm not sure if I'm understanding the question fully. Are you looking for the linear fit for (a) Dissolution vs Particle Size (grouped by Screen Size), or (b) Dissolution vs Screen Size (grouped by Particle Size).
Jed's response above is best for case (a).
If case (b), change Screen Size to Numeric/Continuous, plot Dissolution vs Screen Size, and drag API Particle Size to Group X.
I see, I think I understand your question better now. The reason the example Tablet Production data set won't allow a polynomial fit is because the Screen Size data has a modeling type of Nominal. If you change that to Continuous, then a polynomial fit is possible. See the lower left portion of the image below -> change the degree of the fit to quadratic, for example, to get a quadratic fit instead of linear.
As long as your data type is numeric, and it makes sense to set the modeling type to Continuous, then a polynomial fit is possible.
(Note that you will want to use the Line of Fit graph for this, not the Smoother. These two options have similar looking icons but work very differently, especially for continuous vs nominal data.)
Regarding your request to have the API Particle Size as the X-Aixs, that is tricky. Because Particle Size is not a number, but a category, it is not possible to make a polynomial fit with it. The X-Axis needs to be a number.
If it's just a matter of moving the labels to the bottom of the graph instead of the top, that can be done by right-clicking on the group labels and selecting X Group Edge -> Bottom.
