Sophie Osborne Posted December 8, 2021 Share Posted December 8, 2021 I'm wanting to plot a straight line of best fit onto some scatter plots. I can do this quite easily using the straight line option in lines and curves, however it won't necessarily go through the origin, which I need it to do. I am wanting it to be able to change as I apply filters, so I can't just use the curve draw option, with a set slope (i.e y=bx). I am thinking that I would need to use either a data function or expression function. Is this possible and if so how Link to comment Share on other sites More sharing options...

Fabian Duerr Posted December 9, 2021 Share Posted December 9, 2021 You can achieve this with a data function. The function will take your filtered data as input. The output could be a new table with the original values and the simulated values from the regression. You can use the nls() function instead of the lm() function in R to force the intercept to 0. See an example here: https://alvaroaguado3.github.io/forcing-regression-coefficients-in-r-par... If a regular linear regression on your data has an intercept that is already very close to 0 you could also run the lm() function to extract the slope. This would shift your line slightly. I can't estimate this effect without knowing your data. If you have never worked with data functions before you can watch two little video tutorials that I posted here: https://community.spotfire.com/questions/self-referential-calculated-column https://community.spotfire.com/questions/adding-value-previous-row-current-... You might find more tutorials in youtube or other places Link to comment Share on other sites More sharing options...

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