Hi, To to test whether my regression model meets the assumption of homoscedasticity, I would like to perform a graphical analysis using a plot. This is what i did so far:

model <- lm(Umsatz~Patente+Marken+Konkordanz+MA+Arbeitsproduktivität, data=data_xls
plot(fitted.values(model),rstandard(model))
plot(model,1)
Then I got the first plot in the picture:

In order to be able to compare it with my other plot (the second plot on the picture) I would like to scale the axes similarily. Unfortunately, I could not figure out how to scale my x-axis from 18 to 25 and my y-axis from -0.5 to 1.5.

Would be very happy if someone could help me out here.

This works for this plot just fine. But how do I get different axes for
plot(model,1) (meaning the plot including the red line)?
When I try the xlim and ylim arguments like this:

I treid this without the 4th clsoing bracket
> plot(model, 1,

xlim = c(55,90),ylim = c(-2,2.5))

But I still get an error: Error in plot.default(yh, r, xlab = l.fit, ylab = "Residuals", main = main, :
formal argument "ylim" matched by multiple actual arguments