# eval Function in R (2 Examples)

This tutorial shows how to evaluate expressions with the eval() function in the R programming language.

## Example 1: Apply eval Function to Expression Object

Example expression:

my_expression <- expression(3 + 8) # Create example expression my_expression # expression(3 + 8) |

my_expression <- expression(3 + 8) # Create example expression my_expression # expression(3 + 8)

Application of eval function:

eval(expression(3 + 8)) # Apply eval function to expression # 11 |

eval(expression(3 + 8)) # Apply eval function to expression # 11

The RStudio console returns 11, i.e. the result of our example expression 3 + 8.

## Example 2: Apply eval Function to Character String

Example character string:

my_expression_string <- "3 + 8" # Create string containing expression my_expression_string # "3 + 8" |

my_expression_string <- "3 + 8" # Create string containing expression my_expression_string # "3 + 8"

If we want to evaluate an expression stored as character string, we need to combine the eval function with the parse function:

eval(parse(text = my_expression_string)) # Combined application of eval & parse # 11 |

eval(parse(text = my_expression_string)) # Combined application of eval & parse # 11

## 2 Comments. Leave new

Need a page to explain the differences among:

eval

parse

expression

text

Hey Lee,

Thank you for the comment! Unfortunately, I don’t have such a comparison page yet. You may have a look at this tutorial, though. It explains how to use the parse function in combination with the eval function.

Regards,

Joachim