What is an annotated dataframe really?

Question

I'm a new SO user but also new(-ish) at R. I've recently encountered annotated dataframes. I've tried to do my due diligence in searching for a good explanation and I have read the following about Annotated DataFrames https://www.rdocumentation.org/packages/Biobase/versions/2.32.0/topics/AnnotatedDataFrame. But I don't get what an AnnotatedDataFrame is.

Is it effectively a list of two dataframes (one metadata and the other data)?

Apologies for the annoying question, but it's not clear to me what I'm working with. Any clarification is appreciated. Thank you!

Answer 1

as you have read the documentation,

Description. An AnnotatedDataFrame consists of two parts. There is a collection of samples and the values of variables measured on those samples. There is also a description of each variable measured. The components of an AnnotatedDataFrame can be accessed with pData and varMetadata .

Annotation-dataframe is basically the concept we use in data manipulation, I mention an example and I hope it will get clear for you.

Imagine you have 10 articles(of a website) and you want to do analysis on them, like finding how many nouns are used for each word in each article, how many adjectives and so on. so first you separate each word from articles and put them in their designated rows, then what? then you have a list of words but you need to map them to a field that works as meta so that you can run a trained machine learning model on those to know which words are what, in preparation of doing that you need to convert your data into a data that is now annotated which we call Annotated-Dataframe.