Fixing margins in ggplot2 - r

Question

I have a plot whose margins are slightly askew and need to be removed. So there should be no empty grey along the bottom or at the left and right of the plot. The dots should go right against the axis's. I think part of the problems may be my last two annotation lines. I tried adding + theme(plot.margins = unit(c(0.1,0.1,0.1,0.1), "cm")) in the last line that defines my plot but this just returns an error:
Error: Theme element `plot.margins` is not defined in the element hierarchy.
`
pvalplot<-function(var, maintitle) {
pvalall<-as.data.frame(c(t(var)))
pvalall$Sample_Size<-c((1:(5*162)),(1:(11*162)),(1:(3*162)),(1:(5*162)),(1:(13*162)),(1:(3*162)),(1:(5*162)))
pvalall$Domain<-c(rep("Physical",5*162),rep("Perinatal",11*162),rep("Developmental",3*162),
rep("Lifestyle-Life Events",5*162),rep("Parental-Family",13*162),rep("School",3*162),
rep("Neighborhood",5*162))
pvalall$Domain <- factor(pvalall$Domain,
levels = c("Physical", "Perinatal", "Developmental",
"Lifestyle-Life Events", "Parental-Family",
"School","Neighborhood"))
pvalall[,1]<-ifelse(pvalall[,1]<1e-20,1e-20,pvalall[,1])
names(pvalall)[1]<-"P-Values"
pvalexp.labels= rep("",45*162)
for (i in c(1:45)){
j=i*162-81
pvalexp.labels[j]=rownames(var)[i]
} #makes list of empyt labels that w
p<-ggplot(pvalall,aes(x = 1:nrow(pvalall), y = -log10(pvalall[,1])))+
geom_point(aes(color = Domain,size=5),
alpha = 0.7, size=1)
p+ylab(expression(atop(" -log10(P-Values)")))+
ylim(0,20)+
xlab(element_blank())+
theme(legend.title=element_blank())+
scale_x_continuous( breaks=c(1:45)*162-81, labels = rownames(var))+
theme_classic()+
theme(axis.title.x = element_blank())+
theme(axis.ticks.x = element_blank())+
theme(axis.title.y = element_text(size = 25))+
theme(text = element_text(size=25))+
theme(legend.title=element_blank())+
theme(legend.position=c(0.8,0.7))+
geom_abline(slope=0,intercept=-log10(c(var)[astsa::FDR(c(var))]),linetype = "dashed")+
geom_abline(slope=0,intercept=5.2,linetype = "dashed")+
ggtitle(maintitle)+
theme(plot.title = element_text(hjust = 0.5))+
theme(
legend.box.background = element_rect(),
legend.box.margin = margin(6, 6, 6, 6))+
theme_update(axis.text.x = element_text(angle = 35, size = 6.5, vjust = 1, hjust=1, color = "black")) +
annotate("text", label = expression(paste("FDR P-value","=0.05")),size=5, x=1000,y=-log10(c(var)[astsa::FDR(c(var))])-0.5, color="black",parse=TRUE)+
annotate("text", label = expression(paste("Bonferroni P-value","=0.05")),size=5, x=1200,y=5.7, color="black",parse=TRUE)
}#end of plotting

Answer 1

You can insert a line
scale_y_continuous(expand = c(0, 0)) +
in your plot command chain.