Hello,
The other problem with the boxplot question is that it's ill defined.
Those data[,1], ..., data[, n] variables, what are they? All of them
numeric? If so, then where is the factor?
Some time ago there was a question on multiple boxplots with cut()
defining the factor. I wrote a beneral purpose function as an answer:
https://www.stat.math.ethz.ch/pipermail/r-help/2012-July/317991.html
# Example use.
n <- 200
set.seed(1920)
ID <- rep(LETTERS[1:4], n/4)
x <- matrix(runif(3*n, max=rep(c(2, 1, 1.5), each=n)), ncol=3)
DF <- data.frame(ID=ID, x=x)
cols <- grep("x", names(DF)) # something variable
multi.boxplot(DF[, cols], DF$ID, col = rainbow(3))
Hope this helps,
Rui Barradas
Em 08-08-2012 14:43, S Ellison escreveu:
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
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