Extract field and values from a string in R

Question

I am having this string:

x <- '[{"code":"B1182","description":"Tire pressure monitor module","faultInformations":[{"description":"---"},{"description":"TRUE","description_eng":"TRUE","description_fre":"TRUE","description_ger":"TRUE","description_spa":"TRUE","description_ita":"TRUE","description_tur":"TRUE"}],"freezeFrames":[],"enhancedDtcInfos":[],"status":"ACTIVE","system":"MULTIFUNCTION","systemMeta":{"systemName":null,"subSystemName":null},"description_eng":"Tire pressure monitor module","description_fre":"Module de surveillance de la pression des pneus","description_ger":"Reifendrucküberwachung","description_spa":"Módulo de control de la presión de los neumáticos","description_ita":"Modulo monitor di pressione pneumatico","description_tur":"Lastik basıncı izleme modülü"},{"code":"B124D","description":"Sensor, tyre pressure","faultInformations":[{"description":"---"},{"description":"TRUE","description_eng":"TRUE","description_fre":"TRUE","description_ger":"TRUE","description_spa":"TRUE","description_ita":"TRUE","description_tur":"TRUE"}],"freezeFrames":[],"enhancedDtcInfos":[],"status":"ACTIVE","system":"MULTIFUNCTION","systemMeta":{"systemName":null,"subSystemName":null},"description_eng":"Sensor, tyre pressure","description_fre":"Capteur, pression des pneus","description_ger":"Sensor Reifendruck","description_spa":"Sensor de presión del neumático","description_ita":"Sensore, pressione pneumatici","description_tur":"Sensör, lastik hava basıncı"}]'

If we format the style, it would be like this:

[ {
    "code":"B1182",
    "description":"Tire pressure monitor module",
    "faultInformations":[ {
        "description": "---"
    }
    ,
    {
        "description": "TRUE", "description_eng": "TRUE", "description_fre": "TRUE", "description_ger": "TRUE", "description_spa": "TRUE", "description_ita": "TRUE", "description_tur": "TRUE"
    }
    ],
    "freezeFrames":[],
    "enhancedDtcInfos":[],
    "status":"ACTIVE",
    "system":"MULTIFUNCTION",
    "systemMeta": {
        "systemName": null, "subSystemName": null
    }
    ,
    "description_eng":"Tire pressure monitor module",
    "description_fre":"Module de surveillance de la pression des pneus",
    "description_ger":"Reifendrucküberwachung",
    "description_spa":"Módulo de control de la presión de los neumáticos",
    "description_ita":"Modulo monitor di pressione pneumatico",
    "description_tur":"Lastik basıncı izleme modülü"
}

,
{
    "code":"B124D",
    "description":"Sensor, tyre pressure",
    "faultInformations":[ {
        "description": "---"
    }
    ,
    {
        "description": "TRUE", "description_eng": "TRUE", "description_fre": "TRUE", "description_ger": "TRUE", "description_spa": "TRUE", "description_ita": "TRUE", "description_tur": "TRUE"
    }
    ],
    "freezeFrames":[],
    "enhancedDtcInfos":[],
    "status":"ACTIVE",
    "system":"MULTIFUNCTION",
    "systemMeta": {
        "systemName": null, "subSystemName": null
    }
    ,
    "description_eng":"Sensor, tyre pressure",
    "description_fre":"Capteur, pression des pneus",
    "description_ger":"Sensor Reifendruck",
    "description_spa":"Sensor de presión del neumático",
    "description_ita":"Sensore, pressione pneumatici",
    "description_tur":"Sensör, lastik hava basıncı"
}

]

I would like to extract from the previous string the field code and its value.

Note that in this string there are two codes ("code":"B1182" and "code":"B124D"), but this would be iteratively run over thousand of strings where there might be different code numbers.

So, how can I extract all the codes and their values in this string?

It is a valid JSON, you should use a JSON parser. – Wiktor Stribiżew Mar 30 '20 at 10:53 — Wiktor Stribiżew, Mar 30 '20 at 10:53
Try `jsonlite::fromJSON(x)$code`. – Darren Tsai Mar 30 '20 at 10:58 — Darren Tsai, Mar 30 '20 at 10:58

nurandi · Accepted Answer · 2020-03-30T11:06:47.867

Since it is a json string, you can parse it using json parser, eg: jsonlite.

Install it if you don't have

install.packages("jsonlite")

library(jsonlite)

out <- fromJSON(x)
out

#    code                  description                                                     faultInformations freezeFrames enhancedDtcInfos status
# 1 B1182 Tire pressure monitor module ---, TRUE, NA, TRUE, NA, TRUE, NA, TRUE, NA, TRUE, NA, TRUE, NA, TRUE         NULL             NULL ACTIVE
# 2 B124D        Sensor, tyre pressure ---, TRUE, NA, TRUE, NA, TRUE, NA, TRUE, NA, TRUE, NA, TRUE, NA, TRUE         NULL             NULL ACTIVE
#          system systemMeta.systemName systemMeta.subSystemName              description_eng                                 description_fre
# 1 MULTIFUNCTION                    NA                       NA Tire pressure monitor module Module de surveillance de la pression des pneus
# 2 MULTIFUNCTION                    NA                       NA        Sensor, tyre pressure                     Capteur, pression des pneus
#          description_ger                                   description_spa                        description_ita              description_tur
# 1 Reifendrucküberwachung Módulo de control de la presión de los neumáticos Modulo monitor di pressione pneumatico Lastik basinci izleme modülü
# 2     Sensor Reifendruck                   Sensor de presión del neumático          Sensore, pressione pneumatici  Sensör, lastik hava basinci

Then select any columns you want, for example:

out[, c("code","description")]

#    code                  description
# 1 B1182 Tire pressure monitor module
# 2 B124D        Sensor, tyre pressure

Extract field and values from a string in R

1 Answers1