Adding "empty space" to perimeter of ggplot2 plot

I have a figure that looks like this:
Initial Plot

I am trying to increase the size of the asterisks, using this code:

ggplot(data, aes(x = Cohort, y = C1M_HP, fill = Cohort)) + geom_violin(width = 0.5) +
geom_boxplot(outlier.shape = NA, width = 0.2, coef = 0) + 
geom_signif(comparisons = list(c("Control","Dup")), map_signif_level=TRUE, textsize = 6.25) + 
scale_fill_manual(values = c('#AED6F1', '#F1948A')) + theme_minimal() + 
geom_jitter(alpha = 0.8, width = 0.1)

Unfortunately, this results in the asterisks getting cut off, like so:
Increased asterisk size

I have tried using plot.margin to change the margin sizes, but this is not correct.

How do I add extra ’empty space’ around the edges of my plot to prevent this issue?

>Solution :

One way is to use coord_cartesian(ylim = c(ymin, ymax))

library(ggplot2)
library(ggsignif)

ggplot(mtcars, aes(x = factor(am), y = mpg, fill = factor(am))) + geom_violin(width = 0.5) +
  geom_boxplot(outlier.shape = NA, width = 0.2, coef = 0) + 
  geom_signif(comparisons = list(c("0","1")), map_signif_level=TRUE, textsize = 10.25) + 
  scale_fill_manual(values = c('#AED6F1', '#F1948A')) + theme_minimal() + 
  geom_jitter(alpha = 0.8, width = 0.1)+
  theme_minimal()+
  coord_cartesian(ylim = c(0, max(mtcars$mpg)+5))