Replacing one value in a large csv of floats with a string

[mikel8]

Hey all, I am trying to write a single string to one cell in a large CSV made up entirely of numbers Julia reads in as Floats when copying the CSV into a dataframe. I want to overwrite one value within the csv with a string without changing the rest of the CSV, but due to the rest of the column having type Float64 in the dataframe version of the CSV, I have not been able to do so with the standard dataframe accessing by index. Do people have any suggestions as to how I might get around this issue?

[stillyslalom]

You could use a Union type for the column to make assignment of a string a valid operation:

julia> df = DataFrame(a = 1:3, b = rand(3))
3×2 DataFrame
 Row │ a      b
     │ Int64  Float64
─────┼─────────────────
   1 │     1  0.644675
   2 │     2  0.754814
   3 │     3  0.458067

julia> df.b = convert(Vector{Union{Float64,String}}, df.b);

julia> df.b[2] = "zeroish"
"zeroish"

julia> CSV.write("test.csv", df)
"test.csv"

julia> readlines("test.csv")
4-element Vector{String}:
 "a,b"
 "1,0.6446749255742438"
 "2,zeroish"
 "3,0.4580669558867503"