Smoothing formula for ChartType = xlXYScatterSmoothNoMarkers

Question

Is there any reference materials to look up which specific smoothing formula is used for generating the lines of the ChartType = xlXYScatterSmoothNoMarkers? Is it natural cubic splines with knots at marker points? I am trying to code the formula in stata replicating this smooth line. Thanks.

Answer 1

I don't know what formula Excel uses for smoothing, but if you describe what you are ultimately trying to plot, it would be helpful. Here's a Stata example for smoothing:

  sysuse auto, clear

        twoway scatter weight length, mcolor(*.8) || /*
        */  lpoly weight length, || lowess weight length /*
        */ , by(foreign)

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Eric A Booth | [email protected]