Knitr缓存的输出存储在哪里?

问题描述：

在缓存目录中，可以使用lazyLoad来查看块末尾的环境.但是大块的输出(如果编译了文档，将输出)存储在哪里?

In the cache directory, one can use lazyLoad to view the environment at the end of a chunk. But where is the output of the chunk (that will be printed if the document is compiled) stored?

答

使用源代码！

在此处查看源代码https://github.com/yihui/knitr/blob/master/R/cache.R

您可以看到此处已对此机制进行了说明(在new_cache函数中)

You can see that the mechanism is explained here (within the new_cache function)

# when cache=3, code output is stored in .[hash], so cache=TRUE won't lose
# output as cacheSweave does; for cache=1,2, output is the evaluate() list
cache_output = function(hash, mode = 'character') {
  get(sprintf('.%s', hash), envir = knit_global(), mode = mode, inherits = FALSE)
}

即它作为对象存储在knit_global环境`

I.e. it is stored as an object in the knit_global environemnt`

您可以通过ls(knitr::knit_global(), all = TRUE)

即下面的3个简单块

```{r, cache=TRUE}
summary(cars)
```

```{r }
 ls(knitr::knit_global(), all = TRUE)

```


```{r }
 get(ls(knitr::knit_global(), all = TRUE)[1], knitr::knit_global())

```

提供以下输出

summary(cars)
##      speed           dist    
##  Min.   : 4.0   Min.   :  2  
##  1st Qu.:12.0   1st Qu.: 26  
##  Median :15.0   Median : 36  
##  Mean   :15.4   Mean   : 43  
##  3rd Qu.:19.0   3rd Qu.: 56  
##  Max.   :25.0   Max.   :120
 ls(knitr::knit_global(), all = TRUE)
## [1] ".Preview-2b40490e2591_cache/unnamed-chunk-1_766fcb86fd875984b372e3c23210bfad"
## [2] "metadata"
 get(ls(knitr::knit_global(), all = TRUE)[1], knitr::knit_global())
## [1] "\n```r\nsummary(cars)\n```\n\n```\n##      speed           dist    \n##  Min.   : 4.0   Min.   :  2  \n##  1st Qu.:12.0   1st Qu.: 26  \n##  Median :15.0   Median : 36  \n##  Mean   :15.4   Mean   : 43  \n##  3rd Qu.:19.0   3rd Qu.: 56  \n##  Max.   :25.0   Max.   :120\n```"

如果退出R，则可以使用load命令从缓存文件夹中的* .RData文件中加载数据.另外，要输出get的结果，请考虑使用cat，它将把"\ n"转换为行，并且应看起来像原始输出.

If you have exited R, you can load the data from the file *.RData in the cache folder using the load command. Also, to output the result of get, consider to use cat which will turn the "\n" into lines and should look like original output.

Knitr缓存的输出存储在哪里?

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