同志们，能不能帮我解释下下面这条命令中p的意思吗？我不理解。谢谢了！
chisq.test(x, y = NULL, correct = TRUE,
           p = rep(1/length(x), length(x)), rescale.p = FALSE,
           simulate.p.value = FALSE, B = 2000)

其中：

p	a vector of probabilities of the same length of x. An error is given if any entry of p is negative.