dimebucker91 dimebucker91 - 3 months ago 12
R Question

Dealing with multivalued attributes in R - creating columns for each attribute

I have a data set based on events and each event has attributes in JSON format, so for example, a simplified version of the data:

id event attribute
1 23 {'grades':43, 'school':'primary'}
2 49 {}
3 99 {'x':49, 'y':52, 'country':'Japan'}
4 89 {'grades':56}

the attributes are multivalued, and each row has different numbers of attributes. I am guessing that R is probably not the best way to deal with this kind of data, usually I would have an 'attributes' table separately in SQL and join on the event ID to get the attributes and their values. I am wondering if there is an established way of dealing with this problem in R though. I want a way to represent this data so that I can summarise it and group events with the same kind of attributes to compare their values

update following the suggestion, I'd like to know if there is a straight forward way of getting the result

d = data.frame(id = 1:4,
event =c(23, 49, 99, 89),
grades = c(43, NA, NA, 56),
school=c("primary", NA, NA, NA))

without manually inputting it

second/third update

I've written this, which seems to work, so I thought i'd share, if there's an easier way to do it please let me know:


#data input
id <- 1:4
event <- c(23,49,99,89)
attribute <- c("{'grades':43, 'school':'primary'}", "{}", "{'x':49, 'y':52, 'country':'Japan'}", "{'grades':56}")

#format for fromJSON
attribute <- gsub("'", '"', attribute)
att <- lapply(attribute, fromJSON)

#distinct attributes
att_names <- unique(unlist(lapply(att, names)))

#store output in list list_atts
list_atts <- list()

for(i in 1:length(att_names)){
j <- lapply(att, "[", paste(att_names[i]))
j <- lapply(j, function(x) ifelse(is.null(unlist(x)) == TRUE, NA, unlist(x))) # convert NULL to NA
list_atts[[i]] <- unlist(j)
names(list_atts)[i] <- paste(att_names[i])

The output here:

> data.frame(list_atts, stringsAsFactors = FALSE)
grades school x y country
1 43 primary NA NA <NA>
2 NA <NA> NA NA <NA>
3 NA <NA> 49 52 Japan
4 56 <NA> NA NA <NA>


You could try:

df %>% 
  mutate(to = strsplit(attribute, ",")) %>%
  unnest(to) %>%
  separate(to, into = c("l", "v"), sep = ":") %>%
  mutate_at(vars(l, v), funs(gsub("[^[:alnum:]]", "", .))) %>%
  spread(l, v, sep = "_") %>%
  select(-attribute, -l_)

Which gives:

#  id event l_country l_grades l_school  l_x  l_y
#1  1    23      <NA>       43  primary <NA> <NA>
#2  2    49      <NA>     <NA>     <NA> <NA> <NA>
#3  3    99     Japan     <NA>     <NA>   49   52
#4  4    89      <NA>       56     <NA> <NA> <NA>