library(openxlsx)
library(ggplot2)
library(gridExtra)
sample1<-read.xlsx("http://kanggc.iptime.org/book/data/stat-1.xlsx") 
mid<-sample1$mid
final<-sample1$final
total<-sample1$total
grade<-sample1$grade
plot1<-ggplot(data=sample1, aes(x=grade)) + geom_bar() + ggtitle("Bar Chart of Grade")+ theme(plot.title = element_text(hjust = 0.5))
marrangeGrob(grobs=list(plot1),nrow=1, ncol=1)