heteroskedasticity plot

[Kathi]

Hello,
to check my model for heteroskedasticity I want to plot the fitted values and the residuals (plot (fitted.values (model), residuals (model)).
But then I always get this error message: Error in match.arg(plot) :
'arg' must be NULL or a string vector
Does anyone know why this is happening and how to fix it?
Thanks a lot!

[technocrat]

If you are using lm()

fit <- lm(mpg ~ drat, data = mtcars)
plot(fit,which = 1)

^{Created on 2023-03-06 with reprex v2.0.2}

Other models may have different methods

[fcas80]

[quote="technocrat, post:2, topic:161429"]

Technocrat, what does 

which = 1 

do here?

[technocrat]

The plot.lm method called by plot() produces six plots and by default four are displayed interactively with prompts. To choose the which flag can be used. Often, a four pane window option is set to show the four defaults in one go.

fit <- lm(mpg ~ drat, data = mtcars)
op <- par(mfrow = c(2,2))
plot(fit)

dev.off()
#> null device