R - Getting warnings: “only the first element is u

Question

I'm trying to use "assign" function, inside a for loop, to assign the value of a file to one variable.

When I call the function, it brings the correct answer but in the end it gives me the following warning messages:

 In assign(fileList, read.csv(fileList[i])) :
 only the first element is used as variable name

If I run > corr("specdata", 129) I can see the correct answer, it can print all the right values, but If I assign the values to any variable for example, it says that this variable is "NULL". An example:

cr <- corr("specdata", 150) 
head(cr)
NULL

It will give me all the values that fit in this criteria but it seems that it can't pass the values to "cr". Other examples:

> class(cr)
[1] "NULL"
> cr
NULL

The code that I'm currently using, if is helpful:

corr <- function(directory, threshold){
    if (directory == "specdata"){ 
        setwd("C:/Users/User/Downloads/specdata")

        fileList <- list.files(pattern="*.csv")
        for (i in 1:length(fileList)){
            fileValues <- assign(fileList, read.csv(fileList[i]))
            okValues <- na.omit(fileValues)
            completeCases <- sum(complete.cases(okValues))
            if (completeCases > threshold) {
                sulfate <- okValues["sulfate"]
                nitrate <- okValues["nitrate"]
                correlation <- cor(sulfate, nitrate,  use="complete.obs", method=c("pearson", "kendall", "spearman")) 
                #print(correlation)

            }

            else if (completeCases <= threshold){
                #print("0")
            }

            i = i+1
        }
    }

    else {
        print("There's no such directory")
    }

}

I'm a begginer on R language, so, if there's any way to fix this issue or to read every single file from a folder and manipulate separately, I'd be glad.

Answer 1

assign is used to do just that, "assign" a value to a variable (up to semantics). I suspect you want

fileValues <- read.csv(fileList[i])