使用 fromJSON 创建 JSON 时有关意外符号的错误消息

Question

这可能是一件容易的事，但我在创建一个带有简单文本输入的简单 JSON 文件时遇到了很多困难。形成错误消息很明显我正在做某事。引号有误，但我不知道是什么。

library(jsonlite)

# Create an example
jsoncars <- toJSON(mtcars[1:2,], pretty=TRUE)
jsoncars

这给出：

[
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.62,
    "qsec": 16.46,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4"
  },
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.875,
    "qsec": 17.02,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4 Wag"
  }
]

现在，我将这段完全相同的文本复制到 fromJSON:

fromJSON("[
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.62,
    "qsec": 16.46,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4"
  },
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.875,
    "qsec": 17.02,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4 Wag"
  }
]")

我收到以下错误：

Error: unexpected symbol in:
"      {
        "mpg"
Execution halted

顺便说一句，fromJSON(jsoncars) 有效，但仍然没有解决我的问题。

有什么想法吗？

Answer 1

使用'与JSON文本中的"区分开来：

jsonlite::fromJSON('[
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.62,
    "qsec": 16.46,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4"
  },
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.875,
    "qsec": 17.02,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4 Wag"
  }
]')

              mpg cyl disp  hp drat    wt  qsec vs am gear carb
Mazda RX4      21   6  160 110  3.9 2.620 16.46  0  1    4    4
Mazda RX4 Wag  21   6  160 110  3.9 2.875 17.02  0  1    4    4

另一种选择是新的 R>=4.0 raw character string 语法 r"(...)":

jsonlite::fromJSON(r"([
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.62,
    "qsec": 16.46,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4"
  },
  {
    "mpg": 21,
    "cyl": 6,
    "disp": 160,
    "hp": 110,
    "drat": 3.9,
    "wt": 2.875,
    "qsec": 17.02,
    "vs": 0,
    "am": 1,
    "gear": 4,
    "carb": 4,
    "_row": "Mazda RX4 Wag"
  }
])")

使用 fromJSON 创建 JSON 时有关意外符号的错误消息

Error message about unexpected symbol while creating JSON with fromJSON

r

jsonlite