CODEWITHSUNDEEP
rassociationscluster-analysissequencerecommendation-engine
Jayanth N Bharadwaj
Jayanth N Bharadwaj

Reputation: 7

Generating sequence data for recommender system in R

I am trying to build a recommender system to recommend electives to the new students based on their core courses and historical students' data (data contain both core courses and electives).

  1. I have the data as shown in this table:

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  1. I generated a cross-table as shown in Table2 (with no order of Term_Code)

enter image description here

  1. I want to generate a sequence data as shown in Table3 (The combination of Course_Num:Grade should be in order with respect to Term_Code

enter image description here

Any help is greatly appreciated. Thanks in advance!

Upvotes: 0

Views: 75

Answers (3)

Andrew Lavers
Andrew Lavers

Reputation: 4378

Using reshape2 and %>% operator from dplyr

df <- read.csv(text="
Student_Num,1000,1100,2000,2200,4100,4200
1,A,B-,,B,,C
2,,B,A,,,
3,,,C,,E,
", stringsAsFactors = FALSE)


library(reshape2)
library(dplyr)

melt(df, id.vars = "Student_Num",  value.name = 'Grade') %>%
  mutate(variable = substr(variable, 2, 5)) %>%
  filter(Grade != "") %>%
  group_by(Student_Num) %>%
  summarize(Sequence = paste0(variable, ":", Grade, collapse = ","))

#  Student_Num Sequence                    
#        <int> <chr>                       
# 1           1 1000:A,1100:B-,2200:B,4200:C
# 2           2 1100:B,2000:A               
# 3           3 2000:C,4100:E

Upvotes: 0

Melissa Key
Melissa Key

Reputation: 4551

Using the tidyverse suite of packages:

library(tidyverse)

# The pipe operator (%>%) makes df1 the first argument of the next function.
# It lets us look at this "in order" not nested
df1 <- data_frame(
  term_code = c(200701, 200701, 200707, 200701, 200801, 200807, 200707, 200701), 
  student_number = rep(1:3, c(4, 2, 2)),
  course_number = c(1000, 2200, 1100, 4200, 2000, 1100, 2000, 4100),
  grade = c('A','B', 'B-','C','A', 'B','C','E')
)

df1 %>%
  unite(Sequence,c(course_number, grade), sep = ":") %>%
  group_by(student_number) %>%
  summarize(
    Sequence = paste(Sequence, collapse = ", ")
  )

If you aren't familiar with the pipe operator or the other functions I'm using, I would call this one piece at a time so you can see what it's doing (and it's all documented at https://www.tidyverse.org/). For example,

df1 %>%
  unite(Sequence,c(course_number, grade), sep = ":")

Upvotes: 1

IceCreamToucan
IceCreamToucan

Reputation: 28695

It would probably be easier to start from Table 1 (df1 in example below)

require(dplyr)
set.seed(46)

df1 <- data.frame(Term_Code = sample(2001:2003, 7, T),
                 Student_Num = sample(1:3, 7, T),
                 Course_Num = sample(1000:1003, 7, T),
                 Grade = sample(LETTERS[1:4], 7, T), stringsAsFactors = F)

# A tibble: 7 x 5
# Groups:   Student_Num [3]
#  Term_Code Student_Num Course_Num Grade Sequence
#      <int>       <int>      <int> <chr> <chr>   
#1      2001           2       1003 A     1003:A  
#2      2001           3       1002 D     1002:D  
#3      2002           3       1003 A     1003:A  
#4      2002           1       1000 A     1000:A  
#5      2001           1       1002 B     1002:B  
#6      2002           2       1002 B     1002:B  
#7      2003           1       1003 A     1003:A

df1 %>% 
    group_by(Student_Num) %>% 
    summarise(Sequence = paste(Course_Num, Grade, sep = ':', collapse = ', '))

# A tibble: 3 x 2
#  Student_Num Sequence              
#        <int> <chr>                 
#1           1 1000:A, 1002:B, 1003:A
#2           2 1003:A, 1002:B        
#3           3 1002:D, 1003:A

Upvotes: 1

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