最近在做多样性分析的时候，代码总是报错，错误为Error in as.data.frame.default(x[[i]], optional = TRUE) :
  cannot coerce class ‘"function"’ to a data.frame，但是之前是可以运行的，数据换了很多格式还是不行，所以请各位大佬指点，到底是啥原因，多谢大佬！
代码如下：
setwd("D:/RDATA")
otu <- read.csv('7samplespearman.csv', row.names = 1, sep = '\t', stringsAsFactors = FALSE, check.names = FALSE)
otu <- t(otu)
library("vegan")
library("picante")
alpha <- function(x, tree = NULL, base = exp(1)) {
  est <- estimateR(x)
  Richness <- est[1, ]
  Chao1 <- est[2, ]
  ACE <- est[4, ]
  Shannon <- diversity(x, index = 'shannon', base = base)
  Simpson <- diversity(x, index = 'simpson')   
  Pielou <- Shannon / log(Richness, base)
  goods_coverage <- 1 - rowSums(x == 1) / rowSums(x)
  result <- data.frame(Richness, Shannon, Simpson, Pielou, Chao1, ACE, goods_coverage)
  if (!is.null(tree)) {
    PD_whole_tree <- pd(x, tree, include.root = FALSE)[1]
    names(PD_whole_tree) <- 'PD_whole_tree'
    result <- cbind(result, PD_whole_tree)}
  result}
write.csv(alpha, 'D:/RDATA/otu_alpha.csv', quote = FALSE)
Error in as.data.frame.default(x[[i]], optional = TRUE) :
  cannot coerce class ‘"function"’ to a data.frame