install.packages("qqman",repos="http://cran.cnr.berkeley.edu/",lib="~" ) # location of installation can be changed but has to correspond with the library location 
library("qqman",lib.loc="~") 
results_log <- read.table("logistic_results.assoc_2.logistic", head=TRUE)
jpeg("QQ-Plot_logistic.jpeg")
qq(results_log$P, main = "Q-Q plot of GWAS p-values : log")
dev.off()

results_as <- read.table("assoc_results.assoc", head=TRUE)
jpeg("QQ-Plot_assoc.jpeg")
qq(results_as$P, main = "Q-Q plot of GWAS p-values : log")
dev.off()