First thing; are you trying to fit a model specified as
y ~ X + X^2 + X^3 ?
... because if you are you're unlikely to get anything useful. That uses formula syntax in which ^ does not have the arithmetic power meaning; see section 11.1 'Defining statistical models; formulae' in 'an introduction to R' in your HTML help system. This formula only specifies one term, X, so all you'll get is the result of
y ~ X
If you wanted to fit a polynomial the hard (and not generally good) way you'd have to do
y ~ I(X )+ I(X^2) + I(X^3)
Next, in your line
fit <- lm(Y~conditional.argument)
you have asked lm to fit Y to a character string formed by paste(). That is also unlikely to be useful. You would need to create the complete formula as a string (eg "Y~X+I(X^2)+I(X^3)" ) and then use as.formula to convert that to a formula lm can use.
Then there's the unnecessary loop. You can get your formula string without a loop from an integer 'degree' using
formstring <- paste("Y ~ ", paste("I(X^",1:degree,")" , sep="", collapse=" + "))
And then you can convert formstring to a formula object and use the formula object in lm:
form <- as.formula(formstring) #be careful with this; it looks for the terms in the current environment...
lm(form)
Or, if 'degree' were a vector (say
degree<-c(1, 3, 5)
formstring <- paste("Y ~ ", paste("I(X^",degree,")" , sep="", collapse=" + "))
and so on.
I am having this problem as well when I want to do a boxplot
with variable number of groups to compare.
I don't know what you're trying to achieve with boxplot, but if you gave boxplot itself your vectors it would plot them by itself:
x<-rnorm(17)
y<-runif(23)
z<-c(x,y)
boxplot(x,y,z)
Incidentally, this:
conditional.argument <- data[,1], data[,2], ...,data[,nvariables] #
is not a valid assignment in R, so it cannot be the code you used. And using something called 'data' (or any other object) in a function that does not have an named argument by the same name is asking for trouble; there is no telling where it will get 'data' from but there is a very good chance it will sometimes be from somewhere you don't expect.
S Ellison
-----Original Message-----
I am sure that my approach is kind of stupid but I cannot
think of another way to do it. I apologize...
foo <- function(..., degree=..){
degree<-3 # example
conditional.argument <- rep(NA,degree)
for(i in 1:(degree-1)) conditional.argument[i] <-
paste("X^",i,"+",sep="")
conditional.argument[degree] <- paste("X^",degree,sep="")
conditional.argument <- paste(conditional.argument,collapse="")
conditional.argument
# "X^1+X^2+X^3"
fit <- lm(Y~conditional.argument)
...
return(fit)
}
I know that there is the poly() function which I am not looking for.
I am having this problem as well when I want to do a boxplot
with variable number of groups to compare.
multiple.boxplot <- function(...,nvariables){
conditional.argument <- data[,1], data[,2],
...,data[,nvariables] #
should look like that in the end
boxplot(conditional.argument)
}
Can anyone give me a hint?
Daniel Hoop
--
View this message in context:
http://r.789695.n4.nabble.com/Pass-Conditional-loop-argument-i
nto-a-function-tp4639580.html
Sent from the R help mailing list archive at Nabble.com.