Expression: parse + eval - R Full Tutorial

R - Expression: parse + eval

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Execute code in string format In this exemple, we want to execute code which is stored in a string format. `# the string str <- "1+1" # A string is not an expression. is.expression(str) [1] FALSE eval(str) [1] "1+1" # parse convert string into expressions parsed.str <- parse(text="1+1") is.expression(parsed.str) [1] TRUE eval(parsed.str) [1] 2` Remarks The function `parse` convert text and files into expressions. The function `eval` evaluate expressions.

Execute code in string format

In this exemple, we want to execute code which is stored in a string format.

# the string
str <- "1+1"

# A string is not an expression.
is.expression(str)
[1] FALSE

eval(str)
[1] "1+1"

# parse convert string into expressions
parsed.str <- parse(text="1+1")

is.expression(parsed.str)
[1] TRUE

eval(parsed.str)
[1] 2

Remarks

The function parse convert text and files into expressions.

The function eval evaluate expressions.

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