Graph

ggplot(data = exp, mapping = aes(x = run, y = par, group=run)) + geom_boxplot() + ggtitle("PAR of thalli before each experiment")+ theme(plot.title = element_text(size = 12, face = "plain")) +theme(axis.text=element_text(size=12),axis.title=element_text(size=12,face="plain")) + ylab("PAR") + xlab("Experimental Run") + theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(), panel.background = element_blank(), axis.line = element_line(colour = "black")) 
## Warning: Removed 120 rows containing non-finite values (stat_boxplot).