Remi.b Remi.b - 5 months ago 55
R Question

Evaluate strings for regression

From these strings

data = "mtcars"
y = "mpg"
x = c("cyl","disp")

, I am trying to perform a linear model. I tried things like

epp=function(x) eval(parse(text=paste0(x,collapse="+")))

# Error in eval(expr, envir, enclos) : object 'cyl' not found

where the last line was aimed to be equivalent to


42- 42-

This involves two operations that are both described in multiple SO entries that use perhaps singly either the get or as.formula functions:

   formula=as.formula( paste( y, "~", paste(x, collapse="+") ) )

In both cases you are use a text/character object to return a language object. In the first argument get returns a 'symbol' that can be evaluated and in the second instance as.formula returns a 'formula' object.