In R, nested loops don't return the expected result while reading through multiple files

Question

Objective: calculate correlation coefficients between 2 variables for multiple files that meet the custom criterion for complete cases (threshold argument).

Data: 332 .csv files in a specified directory.

Desired output: vector with correlation coefficients for the files.

Code:

 correl <- function(directory = "~/specdata/specdatacsv", threshold = 0) {
  filelist <- list.files(path = directory, pattern = ".csv", full.names = TRUE)
  nobs <- numeric()
  corrvector <- numeric()
  
  for(i in length(filelist)) {
    data <- read.csv(filelist[i])
    nobs <- sum(complete.cases(data))
    if (nobs <= threshold) { next
    } else {
      nitrate <- as.vector(data$nitrate)
      sulfate <- as.vector(data$sulfate)
      goodSulfate <- complete.cases(sulfate)
      goodNitrate <- complete.cases(nitrate)
      icorr <- cor(goodNitrate, goodSulfate)
      corrvector <- c(corrvector, icorr)
    }
  }
  corrvector
}

The output for the threshold 150 should return:

[1] -0.01895754 -0.14051254 -0.04389737 -0.06815956 -0.12350667 -0.07588814

But instead the empty corrvector gets returned. Please, help me find the mistake I've made.