Toy examle of using agrep to match food groups for participant food choices

cofid_groups_toy_example.R

library(tidyr)

# User data dataframe
user.foods = rbind("milk", "apples", "bread", "ice cream", "boxed fruits")
ID = rbind(1, 2, 3, 4, 5)
user.data = cbind(ID, user.foods)
colnames(user.data) = c("ID", "User.Food")
user.data = as.data.frame(user.data)

# Food Groups dataframe
foods = rbind("Cream", "Milk", "Yoghurt", "Bread", "Ice cream cones", 
              "Orange", "Carrots", "Milk chocolate")
foodcodes = rbind("Dairy", "Dairy", "Dairy", "Grains", "Dairy", 
                 "Fruit and vegetables", "Fruit and vegetables", "Sweets")
food.groups = cbind(foods, foodcodes)
colnames(food.groups) = c("Food", "Food.Code")
food.groups = as.data.frame(food.groups)

# Find row indexes from food.groups that match pattern
match.food = function(pattern){
        matches = agrep(pattern, food.groups$Food, ignore.case = TRUE, 
                        value = FALSE)
        return(matches)
}

# Add matched indexes to user data
user.data$matched.indexes = sapply(user.data$User.Food, FUN=match.food)

# Convert the no matches (which is a list with zero in) to NA
check = function(x) {
     if(sum(x) == 0) {
         return(TRUE) 
     } else {
         return(FALSE)
     }
}
user.data[sapply(user.data$matched.indexes, check), ]$matched.indexes = NA

# Convert to long format
long.user.data = separate_rows(user.data, matched.indexes, convert=FALSE)

# Filter out the weird "c" and "" entries that separate_rows add because
# apparently no one has ever come across a situation where a cell contains an
# actual list and not a list in the form of a comma separated string!
long.user.data = long.user.data[long.user.data$matched.indexes != "c" & 
                                long.user.data$matched.indexes != "" 
                                | is.na(long.user.data$matched.indexes), ]

# Add in the food group data
user.food.matches = cbind(long.user.data, 
                          food.groups[long.user.data$matched.indexes, 
                                      c("Food", "Food.Code"])