创建累积二项分布表

Question

我是R的新手，试图构建一个累积的二项分布表并陷入循环中。

r = readline("please enter an interger n:")

p = seq(from = 0.1, to = 1,by = 0.1 )
r = seq(from = 0, to = 100)

n <- ""
for (each in r) {

 x=qbinom(x,r,p)
}
print(x)

Answer 1

作为循环的替代方法：您可以使用expand.grid创建k和p的所有排列，并进一步避免循环，因为pbinom可以采用向量。

# Create input values
p = 1:9/10
k = 0:25
n = 25

# Create permutations of `k` and `p`: use this to make grid of values
ex <- expand.grid(p=p, k=k)

# Find probabilities for each value set
ex$P <- with(ex, pbinom(k, n, p ))

# Reshape to your required table format
round(reshape2::dcast(k ~ p, data=ex, value.var = "P"), 3)

循环方法

# Values to match new example
p = 1:19/20
k = 0:25
n = 4

# Create matrix to match the dimensions of our required output
# We will fill this as we iterate through the loop
mat1 <- mat2 <- matrix(0, ncol=length(p), nrow=length(k), dimnames=list(k, p))

# Loop through the values of k
# We will also use the fact that you can pass vectors to `pbinom`
# so for each value of `k`, we pass the vector of `p`
# So we will update each row of our output matrix with 
# each iteration of the loop

for(i in seq_along(k)){

     mat1[i, ] <- pbinom(k[i], n, p)

}

为了完整起见，我们可以更新输出矩阵的列 - 即p的每个值都传递向量k

for(j in seq_along(p)){

  mat2[, j] <- pbinom(k, n, p[j])

}

# Check that they give the same result
all.equal(mat1, mat2)