looping to tokenize using text2vec - r

Question

Edited to shorten and provide sample data.
I have text data consisting of 8 questions asked of a number of participants twice. I want to use text2vec to compare the similarity of their responses to these questions at the two points in time (duplicate detection). Here is how my initial data is structured (in this example there are just 3 participants, 4 questions instead of 8, and 2 quarters/time periods). I want to do similarity comparison for each participant's response in the first quarter vs. the second quarter. I intend to use package text2vec's psim command to do this.
df<-read.table(text="ID,Quarter,Question,Answertext
Joy,1,And another question,adsfjasljsdaf jkldfjkl
Joy,2,And another question,dsadsj jlijsad jkldf
Paul,1,And another question,adsfj aslj sd afs dfj ksdf
Paul,2,And another question,dsadsj jlijsad
Greg,1,And another question,adsfjasljsdaf
Greg,2,And another question, asddsf asdfasd sdfasfsdf
Joy,1,this is the first question that was asked,this is joys answer to this question
Joy,2,this is the first question that was asked,this is joys answer to this question
Paul,1,this is the first question that was asked,this is Pauls answer to this question
Paul,2,this is the first question that was asked,Pauls answer is different
Greg,1,this is the first question that was asked,this is Gregs answer to this question nearly the same
Greg,2,this is the first question that was asked,this is Gregs answer to this question
Joy,1,This is the text of another question,more random text
Joy,2,This is the text of another question, adkjjlj;ds sdafd
Paul,1,This is the text of another question,more random text
Paul,2,This is the text of another question, adkjjlj;ds sdafd
Greg,1,This is the text of another question,more random text
Greg,2,This is the text of another question,sdaf asdfasd asdff
Joy,1,this was asked second.,some random text
Joy,2,this was asked second.,some random text that doesn't quite match joy's response the first time around
Paul,1,this was asked second.,some random text
Paul,2,this was asked second.,some random text that doesn't quite match Paul's response the first time around
Greg,1,this was asked second.,some random text
Greg,2,this was asked second.,ada dasdffasdf asdf asdfa fasd sdfadsfasd fsdas asdffasd
", header=TRUE,sep=',')
I've done some more thinking and I believe the right approach is to split the dataframe into a list of dataframes, not separate items.
questlist<-split(df,f=df$Question)
then write a function to create the vocabulary for each question.
library(text2vec)
vocabmkr<-function(x) {
itoken(x$AnswerText, ids=x$ID) %>% create_vocabulary()%>% prune_vocabulary(term_count_min = 2) %>% vocab_vectorizer()
}
test<-lapply(questlist, vocabmkr)
But then I think I need to split the original dataframe into question-quarter combinations and apply the vocab from the other list to it and am not sure how to go about that.
Ultimately, I want a similarity score telling me if the participants are duplicating some or all of their responses from the first and second quarters.
EDIT: Here is how I would do this for a single question starting with the above dataframe.
quest1 <- filter(df,Question=="this is the first question that was asked")
quest1vocab <- itoken(as.character(quest1$Answertext), ids=quest1$ID) %>% create_vocabulary()%>% prune_vocabulary(term_count_min = 1) %>% vocab_vectorizer()
quest1q1<-filter(quest1,Quarter==1)
quest1q1<-itoken(as.character(quest1q1$Answertext),ids=quest1q1$ID) # tokenize question1 quarter 1
quest1q2<-filter(quest1,Quarter==2)
quest1q2<-itoken(as.character(quest1q2$Answertext),ids=quest1q2$ID) # tokenize question1 quarter 2
#now apply the vocabulary to the two matrices
quest1q1<-create_dtm(quest1q1,quest1vocab)
quest1q2<-create_dtm(quest1q2,quest1vocab)
similarity<-psim2(quest1q1, quest1q2, method="jaccard", norm="none") #row by row similarity.
b<-data.frame(ID=names(similarity),Similarity=similarity,row.names=NULL) #make dataframe of similarity scores
endproduct<-full_join(b,quest1)
Edit:
Ok, I have worked with the lapply some more.
df1<-split.data.frame(df,df$Question) #now we have 4 dataframes in the list, 1 for each question
vocabmkr<-function(x) {
itoken(as.character(x$Answertext), ids=x$ID) %>% create_vocabulary()%>% prune_vocabulary(term_count_min = 1) %>% vocab_vectorizer()
}
vocab<-lapply(df1,vocabmkr) #this gets us another list and in it are the 4 vocabularies.
dfqq<-split.data.frame(df,list(df$Question,df$Quarter)) #and now we have 8 items in the list - each list is a combination of question and quarter (4 questions over 2 quarters)
How do I apply the vocab list (consisting of 4 elements) to the dfqq list (consisting of 8)?

Answer 1

I'm sorry, that sounds frustrating. In case you have more to do and did want a more automatic way to do it, here's one approach that might work for you:
First, convert your example code for a single dataframe into a function:
analyze_vocab <- function(df_) {
quest1vocab =
itoken(as.character(df_$Answertext), ids = df_$ID) %>%
create_vocabulary() %>%
prune_vocabulary(term_count_min = 1) %>%
vocab_vectorizer()
quarter1 = filter(df_, Quarter == 1)
quarter1 = itoken(as.character(quarter1$Answertext),
ids = quarter1$ID)
quarter2 = filter(df_, Quarter == 2)
quarter2 = itoken(as.character(quarter2$Answertext),
ids = quarter2$ID)
q1mat = create_dtm(quarter1, quest1vocab)
q2mat = create_dtm(quarter2, quest1vocab)
similarity = psim2(q1mat, q2mat, method = "jaccard", norm = "none")
b = data.frame(
ID = names(similarity),
Similarity = similarity)
output <- full_join(b, df_)
return(output)
}
Now, you can split if you want and then use lapply like this: lapply(split(df, df$Question), analyze_vocab). However, you already seem comfortable with piping so you might as well go with that approach:
similarity_df <- df %>%
group_by(Question) %>%
do(analyze_vocab(.))
Output:
> head(similarity_df, 12)
# A tibble: 12 x 5
# Groups: Question [2]
ID Similarity Quarter Question Answertext
<fct> <dbl> <int> <fct> <fct>
1 Joy 0 1 And another question adsfjasljsdaf jkldfjkl
2 Joy 0 2 And another question "dsadsj jlijsad jkldf "
3 Paul 0 1 And another question adsfj aslj sd afs dfj ksdf
4 Paul 0 2 And another question dsadsj jlijsad
5 Greg 0 1 And another question adsfjasljsdaf
6 Greg 0 2 And another question " asddsf asdfasd sdfasfsdf"
7 Joy 1 1 this is the first question that was asked this is joys answer to this question
8 Joy 1 2 this is the first question that was asked this is joys answer to this question
9 Paul 0.429 1 this is the first question that was asked this is Pauls answer to this question
10 Paul 0.429 2 this is the first question that was asked "Pauls answer is different "
11 Greg 0.667 1 this is the first question that was asked this is Gregs answer to this question nearly the same
12 Greg 0.667 2 this is the first question that was asked this is Gregs answer to this question
The values in similarity match the ones shown in your example endproduct (note that values shown are rounded for tibble display), so it seems to be working as intended.

Answer 2

I gave up and did this manually one dataframe at a time. I'm sure there's a simple way to do it as a list but I can't for the life of me figure out how to apply a list of functions (the vocab vectorizers) to the "Answertext" column in the list of dataframes.
As powerful as R is, a simple for loop that allows text swapping into the command (a la Stata's "foreach") is grossly lacking. I get that there is a different workflow involving breaking a dataframe into a list and iterating over that but for some activities this complicates matters grossly, necessitating complex indexes to refer not just to the list but also to the specific vectors contained in the list. I also recognize that the Stata-like behavior can be achieved using assign and paste0 but this, like most code in R, is terribly clunky and obtuse. sigh.