如何在R中读取嵌套的JSON结构? [英] How to read nested JSON structure in R?

问题描述

我有一些看起来像这样的JSON:

I have some JSON that looks like this:

"total_rows":141,"offset":0,"rows":[
{"id":"1","key":"a","value":{"SP$Sale_Price":"240000","CONTRACTDATE$Contract_Date":"2006-10-26T05:00:00"}},
{"id":"2","key":"b","value":{"SP$Sale_Price":"2000000","CONTRACTDATE$Contract_Date":"2006-08-22T05:00:00"}},
{"id":"3","key":"c","value":{"SP$Sale_Price":"780000","CONTRACTDATE$Contract_Date":"2007-01-18T06:00:00"}},
...

在R中，生成SP$Sale_Price与CONTRACTDATE$Contract_Date的散点图的最简单方法是什么?

In R, what would be the easiest way to produce a scatter-plot of SP$Sale_Price versus CONTRACTDATE$Contract_Date?

我到这为止了

install.packages("rjson")
library("rjson")
json_file <- "http://localhost:5984/testdb/_design/sold/_view/sold?limit=100"
json_data <- fromJSON(file=json_file)
install.packages("plyr")
library(plyr)
asFrame <- do.call("rbind.fill", lapply(json_data, as.data.frame))

但是现在我被困住了...

but now I'm stuck...

> plot(CONTRACTDATE$Contract_Date, SP$Sale_Price)
Error in plot(CONTRACTDATE$Contract_Date, SP$Sale_Price) : 
  object 'CONTRACTDATE' not found

如何进行这项工作?

推荐答案

假设您具有以下JSON文件:

Suppose you have the following JSON-file:

txt <- '{"total_rows":141,"offset":0,"rows":[
  {"id":"1","key":"a","value":{"SP$Sale_Price":"240000","CONTRACTDATE$Contract_Date":"2006-10-26T05:00:00"}},
  {"id":"2","key":"b","value":{"SP$Sale_Price":"2000000","CONTRACTDATE$Contract_Date":"2006-08-22T05:00:00"}},
  {"id":"3","key":"c","value":{"SP$Sale_Price":"780000","CONTRACTDATE$Contract_Date":"2007-01-18T06:00:00"}}]}'

然后，您可以使用jsonlite软件包阅读以下内容:

Then you can read it as follows with the jsonlite package:

library(jsonlite)
json_data <- fromJSON(txt, flatten = TRUE)

# get the needed dataframe
dat <- json_data$rows
# set convenient names for the columns
# this step is optional, it just gives you nicer columnnames
names(dat) <- c("id","key","sale_price","contract_date")
# convert the 'contract_date' column to a datetime format
dat$contract_date <- strptime(dat$contract_date, format="%Y-%m-%dT%H:%M:%S", tz="GMT")

现在您可以绘制:

plot(dat$contract_date, dat$sale_price)

哪个给:

如果您选择不展平JSON，则可以执行以下操作:

If you choose not to flatten the JSON, you can do:

json_data <- fromJSON(txt)

dat <- json_data$rows$value

sp <- strtoi(dat$`SP$Sale_Price`)
cd <- strptime(dat$`CONTRACTDATE$Contract_Date`, format="%Y-%m-%dT%H:%M:%S", tz="GMT")
plot(cd,sp)

给出相同的情节:

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