When checking a correct answer with {gradethis} in a {learnr} tutorial, I'm unsure why the following gets printed after clicking 'Submit Answer':
Last value being used to check answer is invisible. See
?invisiblefor more information.
I'm not sure why this prints; I do not understand the content of ?invisible in this context. I think I've misunderstood how to use {gradethis}. Any ideas?
This is a screen shot:
Here's the contents of my {learnr} .Rmd file:
---
title: "Tutorial"
output: learnr::tutorial
runtime: shiny_prerendered
---
```{r setup, include=FALSE}
library(gradethis)
library(learnr)
tutorial_options(exercise.checker = gradethis::grade_learnr)
knitr::opts_chunk$set(echo = FALSE)
```
Type "Hello" between the quotation marks.
```{r hello, exercise = TRUE}
print("")
```
```{r hello-check}
grade_result(
pass_if(~identical(.result, "Hello"), "That is correct.")
)
```
And here's the session info:
─ Session info ──────────────────────────────────────────────────────────────────────────────
setting value
version R version 3.6.1 (2019-07-05)
os macOS Sierra 10.12.6
system x86_64, darwin15.6.0
ui RStudio
language (EN)
collate en_GB.UTF-8
ctype en_GB.UTF-8
tz Europe/London
date 2020-02-02
─ Packages ──────────────────────────────────────────────────────────────────────────────────
package * version date lib source
assertthat 0.2.1 2019-03-21 [1] CRAN (R 3.6.0)
backports 1.1.5 2019-10-02 [1] CRAN (R 3.6.0)
cli 2.0.1 2020-01-08 [1] CRAN (R 3.6.0)
crayon 1.3.4 2017-09-16 [1] CRAN (R 3.6.0)
digest 0.6.23 2019-11-23 [1] CRAN (R 3.6.0)
evaluate 0.14 2019-05-28 [1] CRAN (R 3.6.0)
fansi 0.4.1 2020-01-08 [1] CRAN (R 3.6.0)
fastmap 1.0.1 2019-10-08 [1] CRAN (R 3.6.0)
glue 1.3.1 2019-03-12 [1] CRAN (R 3.6.0)
gradethis * 0.1.0.9002 2020-02-02 [1] Github (rstudio-education/gradethis@a310ca9)
htmltools 0.4.0 2019-10-04 [1] CRAN (R 3.6.0)
htmlwidgets 1.5.1 2019-10-08 [1] CRAN (R 3.6.0)
httpuv 1.5.2 2019-09-11 [1] CRAN (R 3.6.0)
jsonlite 1.6 2018-12-07 [1] CRAN (R 3.6.0)
knitr 1.26 2019-11-12 [1] CRAN (R 3.6.0)
later 1.0.0 2019-10-04 [1] CRAN (R 3.6.0)
learnr * 0.10.0 2019-11-09 [1] CRAN (R 3.6.0)
magrittr 1.5 2014-11-22 [1] CRAN (R 3.6.0)
markdown 1.1 2019-08-07 [1] CRAN (R 3.6.0)
mime 0.8 2019-12-19 [1] CRAN (R 3.6.0)
promises 1.1.0 2019-10-04 [1] CRAN (R 3.6.0)
R6 2.4.1 2019-11-12 [1] CRAN (R 3.6.0)
Rcpp 1.0.3 2019-11-08 [1] CRAN (R 3.6.0)
rlang 0.4.4 2020-01-28 [1] CRAN (R 3.6.1)
rmarkdown 2.0 2019-12-12 [1] CRAN (R 3.6.0)
rprojroot 1.3-2 2018-01-03 [1] CRAN (R 3.6.0)
rstudioapi 0.10 2019-03-19 [1] CRAN (R 3.6.0)
sessioninfo 1.1.1 2018-11-05 [1] CRAN (R 3.6.0)
shiny 1.4.0 2019-10-10 [1] CRAN (R 3.6.0)
withr 2.1.2 2018-03-15 [1] CRAN (R 3.6.0)
xfun 0.12 2020-01-13 [1] CRAN (R 3.6.0)
xtable 1.8-4 2019-04-21 [1] CRAN (R 3.6.0)
yaml 2.2.0 2018-07-25 [1] CRAN (R 3.6.0)
[1] /Users/matt.dray/Library/R/3.6/library
[2] /Library/Frameworks/R.framework/Versions/3.6/Resources/library