My guess is, that you can get what you want by changing the type of :pubyear to string:
df[:pubyear]=string.(df[:pubyear])
If I am wrong please consider reformating your question according to
My guess is, that you can get what you want by changing the type of :pubyear to string:
df[:pubyear]=string.(df[:pubyear])
If I am wrong please consider reformating your question according to