Parse JSON strings into R list

Question

I have my JSON file and I want to parse it in a list. I wonder if I can parse only the lines with specific string in it? For example

{"app":15c,"device_carrier":"Verizon Wireless"}
{"app":15b,"device_carrier":"Verizon Wireless"}
{"app":15a,"device_carrier":"Verizon Wireless"}

and I want to parse only the lines that have "app":15a I want to have a list with the last line! (The problem is I have a lot of data and my computer can't parse the whole JSON file, and I need only one app)

Hi Smasell, can you provide an example of the JSON you want to parse, the desired output, and what you have tried so far? — Keith Hughitt
– Keith Hughitt, Commented Dec 11, 2016 at 13:17
The most robust way would be to parse everything and then filter the list. Filtering before parsing is much more tedious as the formatting of the JSON might potentially vary. — MrMobster
– MrMobster, Commented Dec 11, 2016 at 13:21
@MrMobster Yeah I now it! I've edited the question! Is it possible without parsing the whole file? — Smasell
– Smasell, Commented Dec 11, 2016 at 13:31

Rafael Toledo · Accepted Answer · 2019-10-06 15:36:32Z

There are ways to optimize the following but it might not be necessary in your case:

library(jsonlite)
library(dplyr)

df <- data_frame()
jsonlite::stream_in(file("/tmp/apps.json"), 
                    function(x) { 
                        df <<- bind_rows(df, filter(x, app=="15b"))
                     })

I made a file that looks like:

{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}
{"app":"15c","device_carrier":"Verizon Wireless"}
{"app":"15b","device_carrier":"Verizon Wireless"}
{"app":"15a","device_carrier":"Verizon Wireless"}

Run that code and you get:

df
## # A tibble: 13 × 2
##      app   device_carrier
##    <chr>            <chr>
## 1    15b Verizon Wireless
## 2    15b Verizon Wireless
## 3    15b Verizon Wireless
## 4    15b Verizon Wireless
## 5    15b Verizon Wireless
## 6    15b Verizon Wireless
## 7    15b Verizon Wireless
## 8    15b Verizon Wireless
## 9    15b Verizon Wireless
## 10   15b Verizon Wireless
## 11   15b Verizon Wireless
## 12   15b Verizon Wireless
## 13   15b Verizon Wireless

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