Using the xts
package, you can try something like this
require(RJSONIO)
require(xts)
json <- "[\n {\n \"1986-03-13\": 0.0034722 \n},\n{\n \"1987-09-21\": 0.0069444 \n},\n{\n \"1990-04-16\": 0.013889 \n},\n{\n \"1991-06-27\": 0.020833 \n},\n{\n \"1992-06-15\": 0.03125 \n},\n{\n \"1994-05-23\": 0.0625 \n},\n{\n \"1996-12-09\": 0.125 \n},\n{\n \"1998-02-23\": 0.25 \n},\n{\n \"1999-03-29\": 0.5 \n},\n{\n \"2003-02-18\": 1 \n} \n]"
data <- data.frame(date = unlist(lapply(fromJSON(json), names)),
value = unname(unlist(fromJSON(json))),
stringsAsFactors = FALSE
)
data <- xts(data$value, as.Date(data$date))
data["1995-01-01::2000-01-01"]
## [,1]
## 1996-12-09 0.125
## 1998-02-23 0.250
## 1999-03-29 0.500