rearrange json

library(rjson)
library(magrittr)
library(plyr)
library(dplyr)

jsonFile = "[{\"speed\":4,\"dist\":2,\"brand\":\"Audi\"},
  {\"speed\":4,\"dist\":10,\"brand\":\"Benz\"},
  {\"speed\":7,\"dist\":4,\"brand\":\"Audi\"},
  {\"speed\":7,\"dist\":22,\"brand\":\"Benz\"},
  {\"speed\":8,\"dist\":16,\"brand\":\"Benz\"}
]"

tmp = fromJSON(jsonFile) %>% lapply(unlist) %>% Reduce(rbind, .) %>%
  data.frame(stringsAsFactors = FALSE) %>%
  transform(dist = as.numeric(as.character(dist)),
            speed = as.numeric(as.character(speed))) %>%
  arrange(dist)
sink("jsonRearrange.json")
## toJSON 轉出來的格式不適用，自己嘗試看看
tmp %>% apply(1, function(x){
    x[sapply(x, class) == "character"] %<>% paste0("\"", ., "\"")
    x[sapply(x, class) == "factor"] %<>% paste0("\"", as.character(.), "\"")
    paste0(paste0("\"", names(x), "\":"), x) %>%
      paste(collapse = ",") %>% paste0("{", ., "}")
  }) %>% paste(.,collapse=",\n") %>%
  paste0("[", ., "]") %>% cat()
sink()
## output:
# [{"speed":4,"dist": 2,"brand":Audi},
# {"speed":7,"dist": 4,"brand":Audi},
# {"speed":4,"dist":10,"brand":Audi},
# {"speed":8,"dist":16,"brand":Audi},
# {"speed":7,"dist":22,"brand":Audi}]



# faster method
library(data.table)
check.numeric <- function(x){
  all(regexpr("^\\d*\\.?\\d*$", as.character(x)) > 0)
}

tmp = fromJSON(jsonFile) %>% unlist() %>% cbind(names(.)) %>%
  data.table() %>% setnames(paste0("X", 1:2)) %>%
  plyr:::splitter_d(.(X2)) %>% llply(select, -X2) %>%
  llply(unlist) %>% do.call(cbind, .) %>% data.table()

tmp %<>% sapply(check.numeric) %>% which() %>%
  names() %>% paste0(., "=as.numeric(", ., ")") %>%
  {within(tmp, eval(parse(text=.)))} %>% arrange(dist)

output_file = tmp %>% mutate(splitter = 1:nrow(.)) %>%
  plyr:::splitter_d(.(splitter)) %>% llply(select, -splitter) %>%
  llply(toJSON) %>% do.call(c, .) %>%
  paste0(collapse = ",\n") %>% paste0("[\n", ., "\n]\n")

sink("jsonRearrange.jason")
cat(output_file)
sink()