I'm a complete R beginner and I've the following question for a project:
Three dice (D_1, D_2, D_3) are rolled and let S be their sum. Use R to:
+ Print all the sequences such that `D_1` and `D_2` are both greater than 4 and `S` < 14.
+ Find the conditional probability that `D_1` ana `D_2` are both greater than 3 given that `S` < 15.
+ Find the probability that either the sum of the first two dice is lower than 6 or that `S` < 7.
I've managed everything bar the last part and I'm sure I'm just doing something silly but my fried brain can't figure out what!
This is my code:
die <- 1:6
rolls <- expand.grid(die, die, die) # sample space of three dice
R <- data.frame(rolls, rowSums(rolls))
colnames(R) <- c("D_1", "D_2", "D_3", "S")
subset(R,R$D_1 >4 & R$D_2>4 & R$S < 14)
##probability S < 15
B<-sum(R$S <15)/(dim(R)[1])
##probability D_1 and D_2 >3 and S<15
A<-sum(R$D_1>3 &R$D_2>3 & R$S <15)/dim(R)[1]
##probability that D_1 and D_2 >3 given S<15
condprob<-A/B
condprob
##probability that D_1+D_2<6 OR S<7
sum(R$D_1+D_2<6|R$S<7)/dim(R)[1]
why wont it recognise D_2 in final line of code?
Any help much appreciated.