例題1を解く > expand.grid(1:6,1:6) Var1 Var2 1 1 1 2 2 1 3 3 1 4 4 1 5 5 1 6 6 1 7 1 2 8 2 2 9 3 2 .... b. 両方が同じ目を出すのは？ tmp <- expand.grid(1:6,1:6); tmp[tmp$Var1==tmp$Var2,] Var1 Var2 1 1 1 8 2 2 15 3 3 22 4 4 29 5 5 36 6 6 =>1/6 c.合計が5以下の確率 tmp <- expand.grid(1:6,1:6); nrow(tmp[tmp$Var1+tmp$Var2<=5,]) [1] 10 => 5/18 d. bまたはcが起きる確率 tmp <- expand.grid(1:6,1:6); nrow(with(tmp, tmp[Var1+Var2<=5 | Var1==Var2,]))/36 [1] 0.3889 別解で tmp <- expand.grid(1:6,1:6); nrow(with(tmp, tmp[Var1+Var2<=5 & Var1==Var2,])) [1] 2 => 1/18 P(b) + P(c) - P(b ^ c) = 1/6 + 5/18 - 1/18 = 7/18 => 0.3899 |