追加多个大数据。表;使用colClasses和fread进行自定义数据强制;命名管道

[This is kind of multiple bug-reports/feature requests in one post, but they don't necessarily make sense in isolation. Apologies for the monster post in advance. Posting here as suggested by help(data.table). Also, I'm new to R; so apologies if I'm not following best practices in my code below. I'm trying.][This is kind of multiple bug-reports/feature r