minor typo

2023/2023-03-09_ProgrammingWithJulia-2/slides/1d-io.md

@@ -94,7 +94,7 @@ using DelimitedFiles
 
 mtx = readdlm("matrix.tsv", '\t', Int, '\n')   # returns a Matrix{Int}
 
-writedlm("matrix.csv", ',')
+writedlm("matrix.csv", mtx, ',')
 ```