When i generate a new rmarkdown file (or open existing rmarkdown-files) and try to run a rmarkdown chunk, i get this error: "Error: attempt to use zero-length variable name". I have Win10 and did a fresh install of R and Rstudio yesterday. What did i miss? Where does this error come from?
```{r cars}
summary(cars)
```
```{r cars} Error: attempt to use zero-length variable name
Putting this as an answer for visibility: this happens if you try to run by selecting all in the Rmd and pressing enter like you would with a normal R script. RStudio tries to run this all as R code, including the markdown parts, leading to the errors you saw.
You can avoid this by running an individual chunk by clicking the green play button or by selecting one of the run options in the dropdown at the top of the Rmd editor.
For me the issue was that I had a missing backtick in the closing code block. In other words, it looked like the following (note that there are only two closing backticks, not three as there should be).
```{r}
# do some stuff
``
So the two backticks were being processed as part of the code block, which is legal code for supplying a variable name such as e.g.
`+`
But since no variable name was provided between the backticks, I was getting the "attempt to use zero-length variable name" error.
The problem could be due to the object being changed in the global environment in an earlier session and that session got saved in the global ennvironment. It is better to not save anything in the global environment, while ending the Rstudio session (or R console). One option would be to call the data(cars) again so that we get the original dataset
---
title: "Untitled"
output:
html_document: default
'html_document:': default
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
```{r cars}
data(cars)
summary(cars)
-output
One option to avoid these kind of surprises is to use the "Don't save" option while quitting the session
check the header's.. very top of the script / page..
---
title: "R Notebook" -->
author: "your_name_here" -->
date: "28/05/2022" -->
output: html_document --> 'notebook' returns 'zero-length' error..
---
from above, change...
output: html_notebook
...to...
output: html_document
I got the same message, my error was to have four backtick in one of the block codes
In my case this issue was caused by copying the sequence "''' {r}" into the R studio document. After manually re-entering this phrase, everything worked fine and I successfully generated a markdown file.
I had the same error. The problem was that comments within the code chunk had missing '#´s. The particular code chunk partially executed, showing the results and a syntax warning (but the markdown did not knit) What happened what that I used the keyboard short cut of 'CTRL+AlT+I" to insert a code chunk and it 'swallowed' the comments. A sneaky error to be sure.
I had the following code in my R Studio to suppress some warnings. What I wanted to do was hide all possible output but still evaluate the code, e.g., hide text output (results='hide'), hide warnings, hide messages
```{r message=FALSE, warning=FALSE, results='hide'}
When I got rid of those lines, I stopped getting the error as well.
Hope that helps.
I still get the same error, could you help? I am trying to copy the code for Iran from https://github.com/timchurches/blog/blob/master/_posts/2020-02-18-analysing-covid-19-2019-ncov-outbreak-data-with-r-part-1/analysing-covid-19-2019-ncov-outbreak-data-with-r-part-1.Rmd.
In R, it's possible to create variables whose names contain spaces, punctuation, parentheses, etc. To do this, we use backticks (`) around the variable name:
> `variable with space and special characters in the name (??!!)` <- 1
> print(`variable with space and special characters in the name (??!!)`)
[1] 1
However, there is a constraint: the variable name must contain at least one character:
> `` <- 1
Error: attempt to use a variable name with zero length
Since ` is also used a lot in Markdown, this can lead to confusing situations. Let's examine some cases.
```{r} lineIf you're positioned on the ```{r} line and press Ctrl+Enter, you'll receive this same error message. Just move the cursor to a line within the code block that you want to run.
{r} "tag" not addedYou can get this error if the {r} tag is forgotten after the initial ```. For example, if you have the block above and press Ctrl+Enter, you will get the error:
```
a <- 1
```
If you change it as shown below, it works:
```{r}
a <- 1
```
I'm not totally sure what happens at the parsing level to lead to this error... But happens so often and so consistently that it deserves a mention here.
```If you miss a backtick at the end of the block, as shown below...
```{r}
a <- 1
``
... and you execute Run current chunk, this error will occur.
Rmarkdown files include documentation in addition to code. If you try to execute them as if they were had code onlu and, for example, there's a block at the beginning of the file, this error message might appear. This can happen if you attempt to run something like R file.Rmd from the terminal or select the entire content of an article in RStudio and press Ctrl+Enter.
These are just a few examples. The possible causes are numerous! In some cases, it might even be bugs in a particular package. Even so, having these cases in mind might help to clarify what's going on.
This approach involves selecting (highlighting) the R code only (summary(pressure)), not any of the backticks/fences from the code chunk. (If you see Error: attempt to use zero-length variable name it is because you have accidentally highlighted the backticks along with the R code........source: https://rstudio-conf-2020.github.io/r-for-excel/rstudio.html
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knitr_1.17and windows 10 – Calldata(cars)and then execute thesummary(cars)– Calldata(cars), it is working? In that case, it could be a problem of saving in the global env. – Call