Common R Shiny Errors – Top Errors & Troubleshooting Steps

If you ever have seen the bold, red text after running a few lines or more of shiny code, you probably have an error in your code. These can be frustrating, because it seems like resolving one of these results in you finding another one. Fortunately, there’s plenty of steps you can take to resolve these. Here are a few common errors which you might encounter when you’re working in R. If you’re fairly new to r, you’ll certainly encounter many of these while you’re learning. Over time, you’ll find ways to be able to overcome these errors and write impeccable R code.

1. Could not find function

Trying to create a graph and saw this message? The most common reason why you might encounter this error message is that you didn’t load the function or install package that the function uses. To <a href=””>install a package</a> in R, you would use the install.packages function, combined with the library function to load the package into R. If you know that you have installed the package, try using the <a href=””>load() r function</a> with the name of the package in the body of the function. The load function does exactly as it’s supposed to, and loads the function you are using into R so that you can use it later on in your code.

2. Syntax errors

Often, developers forget to add an additional parenthesis or may spell something incorrectly in their code. These syntax errors are enough to halt your code. These can become very difficult to pinpoint, and searching for these when you’re done becomes very time-consuming to spot as your files get larger. A suggestion would be to proofread each line before you complete your code. These errors are typically in the form of “Unexpected [character] in [variable]” because there is typically something out of place. In case you were to encounter this error, take a look at your syntax.

Here is an example:

mean(x)) would trigger an unexpected ) error because this function contains an extra right parenthesis that the compiler would not expect. Errors like these can easily be caught with a little bit of proofreading.

3. Cannot Open Connection

These types of errors occur typically when you’re trying to load a file into R, but R cannot find the file. This error is typically generated after using the load() function. If you are seeing this error, then you will want to ensure that your file is located in the working directory you’re using with R. If the file is in the same working directory, you will want to ensure that R has the permissions it needs to access the file. To <a href=””>check the permissions</a> for the current working directory, use the the file.access function.

4. Replacement Has Length Zero

This is a confusing error, but it really means to suggest is that R cannot find data in the variable that’s being accessed. Take a look at your code, you might be trying to initialize values that R cannot find. Imagine that you’re looping through a list, R won’t be able to see the first value of the list because it simply does not exist. To resolve this, remember that R vectors start at the first position. Ensure that you’re beginning from this when you’re looping through a list of values.

5. Object Not Found

This is when you’re trying to tell R to find something, but it’s not able to locate the object that you’re telling it to locate. The easiest way to trigger this error is by misspelling a variable or a function name. For example, you might tell R to print a list of numbers, but the variable name that you’re using to access the list doesn’t exactly match up.

For example,

integers &lt;- c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

The print statement above would return the object not found error because R doesn’t know what to look for. The reason why you would see this error is because the integers variable is misspelled in the print statement.

Another reason why you might be seeing this error is if you were to call print(integers) above before defining the integers list, or if you printed integers without having any variable called integers. Luckily, this error is a fairly easy fix. Just look at your code to determine if it’s one of the above errors.


If you’re new to R Shiny, it can be very difficult to spot errors. The easiest way to save yourself a lot of time in troubleshooting these is to proofread your code line by line as you write it. This will allow you to spot some of the simpler syntax errors that you can easily fix. It’s easier to spot minor errors at the end before it’s time to execute the code.

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