R to JSON: long vs. wide data.frame comparison

edhec_long.json

{
 "date" : [
		"1997-01-31",
		"1997-02-28",
		"1997-03-31",
		"1997-04-30",
		"1997-05-31",
		"1997-01-31",
		"1997-02-28",
		"1997-03-31",
		"1997-04-30",
		"1997-05-31"
	],
	"variable" : [
		"Convertible.Arbitrage",
		"Convertible.Arbitrage",
		"Convertible.Arbitrage",
		"Convertible.Arbitrage",
		"Convertible.Arbitrage",
		"CTA.Global",
		"CTA.Global",
		"CTA.Global",
		"CTA.Global",
		"CTA.Global"
	],
	"value" : [
		0.0119,
		0.0123,
		0.0078,
		0.0086,
		0.0156,
		0.0393,
		0.0298,
		-0.0021,
		-0.017,
		-0.0015
	]
}

edhec_to_JSON.R

### Load and format data
require(PerformanceAnalytics)
data(edhec)
# first 2 columns and first 5 rows of edhec as a data frame
edhec_wide<-data.frame(date=index(edhec),coredata(edhec))[1:5,1:3]
edhec_wide$date<-as.character(edhec_wide$date)
# edhec_wide melted to long format
edhec_long<-melt(edhec_wide,id.vars='date')

# convert to JSON
require(RJSONIO)
cat(toJSON(edhec_wide,pretty=TRUE),file='edhec_wide.json')
cat(toJSON(edhec_long,pretty=TRUE),file='edhec_long.json')

edhec_wide.json

{
	"date" : [
		"1997-01-31",
		"1997-02-28",
		"1997-03-31",
		"1997-04-30",
		"1997-05-31"
	],
	"Convertible.Arbitrage" : [
		0.0119,
		0.0123,
		0.0078,
		0.0086,
		0.0156
	],
	"CTA.Global" : [
		0.0393,
		0.0298,
		-0.0021,
		-0.017,
		-0.0015
	]
}