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)

Application of eval function:

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"

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

2 Comments. Leave new

  • Need a page to explain the differences among:
    eval
    parse
    expression
    text

    Reply
    • 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

      Reply

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