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.

Thanks in advance!