# Plotting friend's heights

names<-c("Adam", "Alice", "Brian", "Barbara", "Charles", "Carla", "Christina", "David")
sex<-c("M","F","M","F","M","F","F","M")
ages<-c(18, 19, 22, 21, 20, 29, 20, 19)
heights<-c(167.5, 160, 170.5, 154, 179, 166, 158, 160.5)
# plot(NULL,axes=FALSE,xlim=c(0,2),ylim=c(min(heights),max(heights)), xlab="",ylab="",main="My friends' heights")
plot(NULL, axes=F, xlim=c(0,2), ylim=c(min(heights),max(heights)), xlab="", ylab="Height (cm)", main="My friends’ heights")
axis(2, c(150, 155, 160,165, 170, 175, 180),at=c(150, 155, 160,165, 170, 175, 180), xpd=NA)

###
sex.as.number<-sex
sex.as.number<-gsub("M",1,sex.as.number)
sex.as.number<-gsub("F",2,sex.as.number)
#sex.as.number
sex.as.number<-as.integer(sex.as.number)
sex.as.number

###
par(mfrow=c(1,2))
plot(NULL, axes=F, xlim=c(0,2), ylim=c(min(heights),max(heights)), xlab="", ylab="Height (cm)", main="My friends’ heights")
axis(2, c(150, 155, 160,165, 170, 175, 180),at=c(150, 155, 160,165, 170, 175, 180), xpd=NA)
colours1<-c("blue","deeppink")
text(c(rep(1,8)),heights,names,col=colours1[sex.as.number])
for(i in 1:8){
arrows(0.65,heights[i],0,heights[i],code= 2, col=colours1[sex.as.number[i]],lwd=2,length=0.07)} # } to end the for loop

# pdf("rplot.pdf") 
# graphics.off() 



###### An alternative way avoiding coercing characters to numeric
###### using ifelse to change "M" and "F" to numbers 1 and 2 in one go
sex.as.number <-NULL
for (i in 1:8)  ifelse(sex[i] == "M", sex.as.number[i]<-1, sex.as.number[i]<-2)
colours1<-c("blue","deeppink")
par(mfrow=c(1,2))
plot(NULL, axes=F, xlim=c(0,2), ylim=c(min(heights),max(heights)), xlab="", ylab="Height (cm)", main="My friends’ heights")
axis(2, c(150, 155, 160,165, 170, 175, 180),at=c(150, 155, 160,165, 170, 175, 180), xpd=NA)
text (c(rep(1,8)), heights, names, col=colours1[sex.as.number])
for (i in 1:8){
arrows(0.65, heights[i], 0, heights[i], code = 2, col=colours1[sex.as.number[i]], lwd=2, length=0.07)
}