I understand your POV but, as I said above in another reply, saving a small array of numbers to file is a very common task which does not require a huge flexibility or high throughput and using a full library there is an overkill. One can argue that my complaint is based on a lack of configurability in writedlm() but I did not expect from it to be flexible or efficient, I expected a simple utility to save data in a human readable format and it failed me.
Do you think that I should download an additional and much more complex package to just create a datafile for pgfplots? I'd have to put this burden on each user of my very small and simple library. I downloaded the package and here is the output:
INFO: Installing CSV v0.1.2
INFO: Installing CategoricalArrays v0.1.3
INFO: Installing Compat v0.21.0
INFO: Installing DataArrays v0.4.0
INFO: Installing DataFrames v0.9.0
INFO: Installing DataStreams v0.1.2
INFO: Installing DataStructures v0.5.3
INFO: Installing FileIO v0.3.1
INFO: Installing GZip v0.3.0
INFO: Installing NullableArrays v0.1.0
INFO: Installing Reexport v0.0.3
INFO: Installing SortingAlgorithms v0.1.1
INFO: Installing SpecialFunctions v0.1.1
INFO: Installing StatsBase v0.13.1
INFO: Installing WeakRefStrings v0.2.0
Fifteen packages to create simple text file with few strings and numbers, and it is very likely that I will never use any other functionality from these packages in my project. I can achieve the same thing with one function call in NumPy (savetxt) or two in MATLAB (fprintf for header and dlmwrite).
The most likely scenario here is that I'll just implement a loop over IOBuffer generating a very long string representing my data. It won't be efficient but it doesn't have to. It won't be elegant but it will keep my library simple and easy to use.