CODEWITHSUNDEEP
rknitrr-markdown
Luca Scrucca
Luca Scrucca

Reputation: 96

Rmarkdown: how to show partial output from chunk?

I have an Rmarkdown document and I would like to show only partial output from a code chunk.

For example, consider the following:

```{r echo=1:2, eval=-2, collapse=TRUE}
mod <- lm(speed ~ dist, data = cars)
summary(mod)
out <- capture.output(summary(mod))
cat(c("[...]", out[9:12], "[...]"), sep = "\n")
```

which produces

mod <- lm(speed ~ dist, data = cars)
## summary(mod)
## [...]
## Coefficients:
##             Estimate Std. Error t value         Pr(>|t|)    
## (Intercept)  8.28391    0.87438   9.474 0.00000000000144 ***
## dist         0.16557    0.01749   9.464 0.00000000000149 ***
## [...]

but what I would like to obtain is

mod <- lm(speed ~ dist, data = cars)
summary(mod)
## [...]
## Coefficients:
##             Estimate Std. Error t value         Pr(>|t|)    
## (Intercept)  8.28391    0.87438   9.474 0.00000000000144 ***
## dist         0.16557    0.01749   9.464 0.00000000000149 ***
## [...]

See the different format of summary(mod).

Upvotes: 1

Views: 1397

Answers (2)

Luca Scrucca
Luca Scrucca

Reputation: 96

Here is the solution for my problem

---
output: html_document
---

```{r, echo=FALSE}
library(knitr)
# the default output hook
hook_output <- knit_hooks$get('output')
knit_hooks$set(output = function(x, options) {
  if (!is.null(n <- options$out.lines)) {
    n <- as.numeric(n)
    x <- unlist(stringr::str_split(x, "\n"))
    nx <- length(x) 
    x <- x[pmin(n,nx)]
    if(min(n) > 1)  
      x <- c(paste(options$comment, "[...]"), x)
    if(max(n) < nx) 
      x <- c(x, paste(options$comment, "[...]"))
    x <- paste(c(x, "\n"), collapse = "\n")
  }
  hook_output(x, options)
    })
```

```{r collapse=TRUE, out.lines = 9:12}
mod <- lm(speed ~ dist, data = cars)
summary(mod)
```

```{r collapse=TRUE, out.lines = 1:3}
summary(mod)
```

```{r collapse=TRUE, out.lines = 17:18}
summary(mod)
```

```{r collapse=TRUE, out.lines = 1:20}
summary(mod)
```

Upvotes: 2

Yihui Xie
Yihui Xie

Reputation: 30104

The knitr example 052 should give you the basic idea: define the output hook, and you can manipulate the text in any way you want.

knitr::knit_hooks$set(output = function(x, options) {
  # manipulate x here
})

Upvotes: 1

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