How to use a dataframe in a function in r - r

Question

I need to insert the variables of a dataframe into a function in r. The function in question is "y=[1- (x1-x2) / x3]". When I write, and enter the variables manually it works, however, I need to use the random numbers from the dataframe.
#Original function
f<-function(x1, x2, x3)
+{}
f<-function(x1, x2, x3)
+{return(1-(x1-x2)/x3)}
f(0.9, 0.5, 0.5)```
#Dataframe function
f<-function(x1, x2, x3)
+{}
f<-function(x1, x2, x3)
+{return(1-(x1-x2)/x3)}
f(x1 = x1, x2 = x2, x3 = x3, DATA = DF)
The first output is ok, however, the second output appears the error message. Error in f(VMB = VMB, VMR = VMR, DATA = DATA1) : unused argument (DATA = DATA1) I know I'm not properly inserting the dataframe into the code, but I'm already circling, can anyone help me?

Answer 1

As the comments suggest, your problem is that the function doesn't contain a data argument. R doesn't know where x1, x2, x3 comes from and will only look at through the global environment trying to find them. If these are contained in a data frame, it doesn't know that it should take them from there, and will fail.
For example
f <- function(x,y,z)
1 + (x-y)/z
f(0.9, 0.5, 0.5)
will work, because it knows where to retrieve the values. So will
x1 <- 0.9
x2 <- 0.5
x3 <- 0.5
f(x1, x2, x3)
because it looks through these environemnts, but
df <- data.frame(x = 0.9, y = 0.5, z = 0.5)
f(x, y, z) #fails
fails, because it doesn't look for them in df. Instead you can use
f(df$x, df$y, df$z)
with(df, f(x, y, z)) #same
which lets R know where to get the variables. (Here i used x, y and z to avoid conflict names)
If this function should always take a data.frame and use columns x1, x2, x3 you could use rewrite it to incorporate this, as below.
f <- function(df){
with(df, 1 + (x1-x2)/x3)
}