如何删除knitr输出中的前缀(索引指示器)[1]? [英] How can I remove the prefix (index indicator) [1] in knitr output?

问题描述

标准R输出看起来像这样

Standard R output looks like this

> 3
[1] 3

要删除前缀 1 ，您可以使用

To remove the prefix 1 you can use

> cat(3)
3

是否有一种方法可以全局删除?还是您必须将cat()包裹起来?

Is there a way to remove this globally? Or do you have to wrap cat() around everything?

此外，我在knitr中使用了此功能，因此，如果没有R全局设置，则可能会有一个knitr宽的设置，我确实看过，但看不到.

有人问为什么要这样做，就像您想要构造一个如下所示的报告那样. [1]只是不需要的，对R用户(也就是听众)没有任何意义.

It was asked why one would want this, something like if you wanted to structure a report like the below. The [1] is just not needed and means nothing to none R users (aka, the audience).

其他信息:在knitr中，您可以使用\ Sexpr {}或r ...来在线评估某些内容，在这种情况下，它不会打印[1].例如，如果您有:

Additional Info: In knitr you can use \Sexpr{} or r ... to evaluate something in line, and in that scenario it doesn't print the [1]. For example if you had:

There are `r sum(mtcars$cyl==6)` cars with 6 cylinders.

您会得到:

有7辆6缸汽车.

作为您的输出，而不是:

As your output, not:

有[1] 7辆6缸汽车.

There are [1] 7 cars with 6 cylinders.

推荐答案

没有什么是不可能的.看看使用针织钩子可以做什么.
玩得开心！
_{^{Rmarkdown脚本要点}}

Nothing is impossible. Take a look at what can be done with knitr hooks.
Have fun!
_{^{Rmarkdown script gist}}

# A Prefix nulling hook.

# Make sure to keep the default for normal processing.
default_output_hook <- knitr::knit_hooks$get("output")

# Output hooks handle normal R console output.
knitr::knit_hooks$set( output = function(x, options) {

  comment <- knitr::opts_current$get("comment")
  if( is.na(comment) ) comment <- ""
  can_null <- grepl( paste0( comment, "\\s*\\[\\d?\\]" ),
                     x, perl = TRUE)
  do_null <- isTRUE( knitr::opts_current$get("null_prefix") )
  if( can_null && do_null ) {
    # By default R print output aligns at the right brace.
    align_index <- regexpr( "\\]", x )[1] - 1
    # Two cases: start or newline
    re <- paste0( "^.{", align_index, "}\\]")
    rep <- comment
    x <- gsub( re, rep,  x )
    re <- paste0( "\\\n.{", align_index, "}\\]")
    rep <- paste0( "\n", comment )
    x <- gsub( re, rep,  x )
  }

  default_output_hook( x, options )

})

knitr::opts_template$set("kill_prefix"=list(comment=NA, null_prefix=TRUE))

正常:

```{r}
print( 1:50 )
```

##  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
## [24] 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
## [47] 47 48 49 50

空前缀

```{r, null_prefix=TRUE}
print( 1:50 )
```

##  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
## 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
## 47 48 49 50

设置为默认值(并删除注释字符串):

Set as default (and remove comment string):

```{r}
knitr::opts_chunk$set(opts.label="kill_prefix")
```

```{r}
print( 1:50 )
```

  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
 47 48 49 50

确保我们不会杀死带有[:digit:]模式的字符串.

Ensure we aren't killing strings with [:digit:] patterns.

```{r}
print( paste0( paste0("[", 1:50), "]" ),quote = FALSE)
```

 [1]  [2]  [3]  [4]  [5]  [6]  [7]  [8]  [9]  [10] [11] [12] [13] [14]
 [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28]
 [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42]
 [43] [44] [45] [46] [47] [48] [49] [50]

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