R help - Apr 2003 - how to use apply with a function created by ourselfs...?

Hi.
I'm a real newbie in R, so
I don't know how to apply, a function created by myself...

prediction<-function(a,b)
{
..
}

to a vector...
It doesn't seem to understand
lapply(vector, prediction())...
Anyone can help me?
Thanks in advance,
ana

By default, arithmetic in R is vectorized, with a scalar being a vector 
of length 1.

Consider the following example:

prediction <- function(a, b)
{
	a+b
}
 > prediction(1:3, 4:6)
[1] 5 7 9

hope this helps, spencer graves

ana kozomara wrote:
> Hi.
> I'm a real newbie in R, so
> I don't know how to apply, a function created by myself...
> 
> prediction<-function(a,b)
> {
> ..
> }
> 
> to a vector...
> It doesn't seem to understand
> lapply(vector, prediction())...
> Anyone can help me?
> Thanks in advance,
> ana
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

..hey thanks for the answer, both of you...
but :-(, I don't seem to have an answer to my problem...
I tried with what u suggested, but it doesn't work yet...
so I will precise it...
I have a data frame...
and I would like to apply the function "prediction" which acts on two
vectors
prediction(linear,ind),
to my data frame,I mean to all the rows of my data frame...
something like a function "Map" in Mathematica...
Shortly, I want to apply function "prediction" to a list of arguments,
not
to a single argument...
I hope now it is more clear...
Thanks for the answers once more,
best regards,
ana
______________________________________________________________________
Original poruka
Od: Peter Dalgaard BSA <p.dalgaard at biostat.ku.dk>
Za: Spencer Graves <spencer.graves at pdf.com>
Tema: Re: [R] how to use apply with a function created by ourselfs...?
Primljena: 20 Apr 2003 22:31:52

Spencer Graves <spencer.graves at pdf.com> writes:
> By default, arithmetic in R is vectorized, with a scalar being a
> vector of length 1.
>
> Consider the following example:
>
> prediction <- function(a, b)
> {
> a+b
> }
>  > prediction(1:3, 4:6)
> [1] 5 7 9
>
> hope this helps, spencer graves
Not sure that was the question... If something else was meant, the
answer might be

lapply(v,prediction,b=5)

or

do.call("prediction",as.list(v))

Rephrasing the question might help...

--
   O__  ---- Peter Dalgaard             Blegdamsvej 3
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

hey thanks a lot...
finally I decided to write my own fonction which will do it...
I was completely lost with rbind, mode="list"...
I find slightely weird the R-kind-of-thinking...:)))
Anyway, i'm trying to acomplish my project in R and not c spirit,
so i'll try what u suggests,
..hey, thanks a lot again...

______________________________________________________________________
Original poruka
Od: Peter Dalgaard BSA <p.dalgaard at biostat.ku.dk>
Za: ANA KOZOMARA <magnolia at absolutok.net>
Tema: Re: [R] how to use apply with a function created by ourselfs...?
Primljena: 21 Apr 2003 11:27:48

"ANA KOZOMARA" <magnolia at absolutok.net> writes:
> ..hey thanks for the answer, both of you...
> but :-(, I don't seem to have an answer to my problem...
> I tried with what u suggested, but it doesn't work yet...
> so I will precise it...
> I have a data frame...
> and I would like to apply the function "prediction" which acts on
two
> vectors
> prediction(linear,ind),
> to my data frame,I mean to all the rows of my data frame...
> something like a function "Map" in Mathematica...
> Shortly, I want to apply function "prediction" to a list of
arguments,
not
> to a single argument...
> I hope now it is more clear...
> Thanks for the answers once more,
> best regards,
> ana
It depends on your prediction function. The best thing is to arrange
that it vectorizes over its arguments, as Spencer Graves suggested.
Then it's just

prediction(df[,1],df[,2])

or, if you want something that works for more than two rows,

do.call("prediction", df)

if your prediction() does not vectorize (i.e. a and b has to be
scalars), you can do two things:

pr.row <- function(row) do.call("prediction",row)
apply(df, 1, pr.row)

or create a vectorized prediction(), as in

pr.vec <- function(a,b)
   sapply(seq(along=a),function(i)prediction(a[i],b[i]))

--
   O__  ---- Peter Dalgaard             Blegdamsvej 3
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907