Smoother lines for ggplot2 This question probably has a simple solution, still the thing is I've written a code to plot  mortality in 2 different groups and that is, death in obese patients vs not obese. Now their are 2 groups t1 and t2 (obese vs normal BMI). The graphs works just fine with this code, I'ts just that I wanted the lines to look smoother and not so jagged. I've tried stat_smooth but just cant get it to work.
Im guessing that the code is longer then necessary. 
allmortality<- read.table(header=TRUE, sep=";", text = 
                  "ar_year;t1_all_estimate;t2_all_estimate
                  ar2001-2002;208.0960242;170.924898
                  ar2003-2004;217.48718;151.6087781
                  ar2005-2006;205.9649097;141.4196023
                  ar2007-2008;212.2112923;135.2787361
                  ar2009-2010;205.628018;136.4582058
                  ar2011-2012;166.5654204;146.9776943")

require(ggplot2)

  ggplot(allmortality, aes(x=ar_year)) + 
  geom_point(aes(y = t2_all_estimate, size=4)) +
  geom_line(aes(y = t2_all_estimate, group=1)) + 
  geom_point(aes(y = t1_all_estimate, size=4)) +
  geom_line(aes(y = t1_all_estimate, group=1)) +
  theme_bw() +  
  theme( legend.position="none",
         axis.text.x = element_text(angle = 45, hjust = 1),
         axis.text=element_text(size=12),
         plot.background = element_blank()
         ,panel.grid.major = element_blank()
         ,panel.grid.minor = element_blank()
         ,panel.border = element_blank()) +
  theme(axis.line = element_line(color = 'black')) +
  ylab("Mortality") +
  xlab("Year") +
  ggtitle("mortality rates in obese vs not obese patients") 


 A: If your entire data follows the pattern from your sample here you could try polynomial regression method with a second order (quadratic) polynomial function.
See the example below:
ggplot(allmortality,aes(x=ar_year)) + 
stat_smooth(aes(y = t1_all_estimate, group=1, colour="Obese"     ), method=lm, formula = y ~ poly(x,2), level=0.95) + #tweak the signifance level suitable for your study
stat_smooth(aes(y = t2_all_estimate, group=1, colour="Normal BMI"), method=lm, formula = y ~ poly(x,2), level=0.95) +
geom_point (aes(y = t1_all_estimate, colour = "Obese"    ), size=4) +
geom_point (aes(y = t2_all_estimate, colour ="Normal BMI"), size=4) +
scale_colour_manual("Treatment", breaks = c("Obese", "Normal BMI"), values = c("blue","red")) +
theme_bw() +  
theme(axis.text.x = element_text(angle = 45, hjust = 1),
      axis.text = element_text(size=12), 
      axis.title.x = element_text(vjust=-0.1),
      axis.title.y = element_text(vjust=+1.1),
      plot.background = element_blank(),
      panel.grid.major = element_blank(),
      panel.grid.minor = element_blank(),
      panel.border = element_blank()) +
theme(axis.line = element_line(color = 'black')) +
ylab("Mortality (nº of patients)") +
xlab("Year") +
ggtitle("Mortality in obese vs not obese patients")


