R cannot find a variable or object with the name you used. This usually means you haven't created it yet, misspelled it, or it exists in a different environment.

R doesn't recognize the function you're trying to call. The package containing it may not be loaded, or the function name is misspelled.

You passed an argument to a function that doesn't accept it. This often happens from typos in argument names or using arguments from a different function.

The package you're trying to load hasn't been installed on your system yet.

The installed package was compiled with a newer version of R than you're running. It may still work, but some features could be unreliable.

The package exists but couldn't be loaded, usually because one of its dependencies is missing or incompatible.

R encountered a character or symbol it didn't expect at that position. This usually means a missing comma, parenthesis, bracket, or operator.

R reached the end of your code but was still expecting more — usually a closing parenthesis, bracket, or brace.

R found two symbols next to each other without an operator or separator between them. Common cause: missing comma, pipe, or operator.

R found a string where it wasn't expected, usually because of a missing comma or operator before it.

There's an extra closing parenthesis that doesn't match any opening parenthesis.

You tried to do math (like +, -, *, /) on something that isn't a number, such as a character string or factor.

A function that expects numbers (like mean, sum, sd) received non-numeric data such as character strings.

R tried to convert one data type to another but failed because the conversion isn't possible or doesn't make sense.

An argument you passed to a function is the wrong type. The function expected one type but received another.

You tried to assign a value to a column or vector, but the length of the new value doesn't match the existing data.

When creating a data frame, the vectors you provided have different lengths and R can't recycle them evenly.

You tried to access an element at a position that doesn't exist — like asking for the 10th element of a 5-element vector.

You tried to select a column that doesn't exist in your data frame, usually due to a typo or wrong column name.

You used $ to access a named element, but the object is a simple vector, not a list or data frame.

You used multi-dimensional indexing (like [row, col]) on an object that doesn't have that many dimensions.

R couldn't open a file or URL. The file might not exist, the path might be wrong, or you don't have permission to access it.

The file path you specified doesn't point to an existing file. The path might be wrong, or the file hasn't been created yet.

The file exists but R doesn't have permission to read or write to it. This is an operating system restriction.

A function requires a specific argument that you didn't provide, and there's no default value for it.

You provided the same argument twice — once by name and once by position, or used the same name twice.

R ran out of memory trying to create a large object. Your data or computation requires more RAM than available.

An if statement or while loop received NA instead of TRUE or FALSE. This happens when the condition evaluates to a missing value.

An if() statement received a vector with multiple values instead of a single TRUE or FALSE. if() only works with single logical values.

You passed the same named argument more than once to a function.

You're operating on two vectors where the longer one's length is not a clean multiple of the shorter one. R will still recycle, but the result may not be what you intended.

Matrix multiplication or a similar operation failed because the dimensions don't match. The number of columns in the first matrix must equal the number of rows in the second.

R tried to convert values to another type (usually numeric) but some values couldn't be converted, so they became NA.

You tried to call something as a function (using parentheses) but it isn't a function. A common cause is accidentally overwriting a built-in function name with a variable.

You tried to use [ ] or $ on a function. This usually means you forgot the parentheses to call the function, or a variable has the same name as a function.

R failed to establish a connection to a file, URL, or database. The resource may not exist or be unreachable.

You tried to access a nested element in a list using [[ ]] but the path doesn't exist — one of the intermediate levels is NULL or missing.

You called a generic function on an object type it doesn't know how to handle. The function exists but has no implementation for your object's class.

The number of values you're assigning doesn't evenly divide into the number of positions being replaced.

The plotting function needs either both x and y vectors, or a single matrix/data frame. You provided something it can't interpret.

You passed an object type that the function doesn't support. Often happens when passing a list where a vector is expected.