# R Error – Multiplication requires numeric/complex matrix/vector arguments

In this R tutorial you’ll learn how to **handle the error message “requires numeric/complex matrix/vector arguments”**.

The post is structured as follows:

Let’s dive right in:

## Creation of Example Data

To start with, we need to create some example data:

data <- data.frame(x1 = 2:7, # Create example data x2 = c(2, 1, 5, 3, 2, 7), x3 = c(0, 3, 9, 1, 2, 1)) data # Print example data

Table 1 shows the structure of our example data: It contains six rows and three columns.

## Example 1: Reproduce the Error – requires numeric/complex matrix/vector arguments

In this example, I’ll explain how to replicate the error message “requires numeric/complex matrix/vector arguments” in R.

Let’s assume that we want to perform a matrix multiplication based on our data. Then, we might try to use the following R syntax:

data_multi <- t(data) %*% data # Try to use data frame # Error in t(data) %*% data : # requires numeric/complex matrix/vector arguments

As you can see, the RStudio console returns the error message “requires numeric/complex matrix/vector arguments”. The reason for this is that our input data has the data.frame class instead of the matrix class. Since the %*% operator cannot handle data frames, it returns an error message.

So how can we solve this problem? That’s what I’ll show next!

## Example 2: Fix the Error – requires numeric/complex matrix/vector arguments

This example illustrates how to avoid the matrix multiplication error “requires numeric/complex matrix/vector arguments”.

For this, we have to convert our data frame object to the matrix type using the as.matrix function:

data_multi <- t(data) %*% as.matrix(data) # Convert data frame to matrix data_multi # Print result

Table 2 shows the output of the previous syntax: The result of our matrix multiplication.

## Video, Further Resources & Summary

Would you like to know more about errors and warning messages? Then you might have a look at the following video of my YouTube channel. In the video, I illustrate the contents of this tutorial.

*The YouTube video will be added soon.*

Besides the video, you could have a look at the related tutorials on my website. Some articles are listed here.

- Matrix Multiplication Error in R: non-conformable arguments
- Error in hist.default : ‘x’ must be numeric
- Calculate Correlation Matrix Only for Numeric Columns in R
- Handling Warnings & Errors in R
- All R Programming Examples

On this page, I have shown how to **deal with the error “requires numeric/complex matrix/vector arguments”** in the R programming language. Don’t hesitate to let me know in the comments, in case you have additional questions and/or comments.

## 2 Comments. Leave new

I am working with the harvad database on german credits for a credit scoring model. I wanted to apply the “nuralnet” function but it gives me the following error: error in neurons[[i]] %*% weights[[i]] : requires numeric/complex matrix/vector arguments.

Taking the advice from your article to the base dedicated to training, I applied:

data_train<- t(train) %*% as.matrix(train) .

but it still gives me the same error.

Hey Michael,

This is really hard to tell without seeing the data and its structure. Could you share the output when you run head(your_data) & str(your_data) ?

Regards,

Joachim