Transform Two Column Data Frame into Quanteda Dictionary Format

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My ultimate goal is to create a quanteda dictionary to use for topic classification on text data.

However, my topic keywords are stored in a somewhat different format: I have a column of about 4000 keywords and a second column that specifies the topic each keyword belongs to. Note that there is no equal number of words for each topic. My data looks like this:

     keywords      topic
[1]  "one"         "number"
[2]  "two"         "number"
[3]  "three"       "number"
[4]  "triangle"    "form"
[5]  "circle"      "form"
[...]

How can I transform my keywords into a (quanteda) dictionary format, i.e. a list that contains named vectors for each topic that contain the keywords for the respective topic?

The list should look like this:

list(number = c("one","two","three"),
     form = c("triangle","circle"))

Any help much appreciated!

Find my approach so far bloew. But it doesn't appear right to me (or working):

# 1) Initialize an empty list of vectors that corresponds to my number of topics & add topic names ("topic_names" is just a vector type chr 1:88 that includes the topic names)

mydictionary <- vector(mode = "list", length = 88) 
names(mydictionary ) <- topic_names

# 2) Create a loop that checks for each keyword to match a topic and adds it to the respective vector of my dictionary

# I got it working for one keyword like this:
if (names(mydictionary [1]) == keyword_list$topic[1]) { # if topic of keyword matches topic vector name
  mydictionary[[1]] <- c(mydictionary[[1]], keyword_list$keywords[1]) #add keyword to topic vector
}

# However, I don't know how to transform this into a loop, since a loop has to check every index of keyword_list for every index of mydictionary and I don't know how to achieve this...
quanteda transformation r dictionary
1 Answers

If your data is in a data.frame like topics (see data section), you can quickly get the data in a list like you want. You can use the function split.

my_dictionary <- split(topics$keywords, topics$topic)
my_dictionary

$form
[1] "triangle" "circle"  

$number
[1] "one"   "two"   "three"

Data:

topics <- structure(list(keywords = c("one", "two", "three", "triangle", 
"circle"), topic = c("number", "number", "number", "form", "form"
)), class = "data.frame", row.names = c(NA, -5L))
user_49851760
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