Regression - Diagnostic - Plot - Scale-Location extension

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A chart of the square root of the absolute standardized residuals by fitted values. Also known as a Spread-Location or S-L plot.


The following example shows the output from running this QScript on a Regression - Poisson RegressionPoisson regression output.


Uses the plot.lm or plot.glm functions from the stats R package.


Belsley, D. A., Kuh, E. and Welsch, R. E. (1980). Regression Diagnostics. New York, NY: Wiley.


includeWeb("QScript R Output Functions");

var is_displayr = (!!Q.isOnTheWeb && Q.isOnTheWeb());
if (!is_displayr)
    if (Q.fileFormatVersion() >= 17.13)
        alert("Please update Q to use this feature from the extension button, or run it from the menu via Create > Regression > Diagnostic > Plot > Scale-Location.");

function main() {

    // The following 2 variables contain information specific to this diagnostic.
    var required_class = "Regression";
    var output_name_suffix = "scale.location";
    var item = checkSelectedItemClass(required_class);
    if (item == null)
        return false;
    var r_name = stringToRName(item.referenceName);

    // The following lines contain the R code to run
    var expression = "plot(" + r_name + ", which = 3)"

    return createROutput(item, expression, output_name_suffix);