How can a function in R handle different types of input?

[stella]

Hi,
 
How can a function in R handle different types of input?
I have written a function, which should calculate the slope from several 3-time-point measurements by linear regression

4 three-time-point-measurements:
x<-cbind(c(1,2,3,4),c(2,3,4,5),c(3,4,5,6))

time points:
time<-c(1,3,9)

function for calculating the slope by linear regression:
fit<-function(xx,t){slope <- coefficients(lm(log(xx) ~ 0 + t))[1]
return(slope)
}
alpha<-fit(x[1,],time)
 
At the moment the function output 'alpha' is calculated for x(x1=1,x2=2,x3=3). I would like to get 'alphas' for all four rows of x without using a for-loop.  If I use 'mapply', I get outputs to very entry of x (12 outputs) instead of four.
 
Thank you very much in advance! Yor help is really appreciated!
Stella
 

[Rui Barradas]

Hello,

stella wrote

Hi,
 
How can a function in R handle different types of input?
I have written a function, which should calculate the slope from several 3-time-point measurements by linear regression

4 three-time-point-measurements:
x<-cbind(c(1,2,3,4),c(2,3,4,5),c(3,4,5,6))

time points:
time<-c(1,3,9)

function for calculating the slope by linear regression:
fit<-function(xx,t){slope <- coefficients(lm(log(xx) ~ 0 + t))[1]
return(slope)
}
alpha<-fit(x[1,],time)
 
At the moment the function output 'alpha' is calculated for x(x1=1,x2=2,x3=3). I would like to get 'alphas' for all four rows of x without using a for-loop.  If I use 'mapply', I get outputs to very entry of x (12 outputs) instead of four.
 
Thank you very much in advance! Yor help is really appreciated!
Stella

It's close to what you were doing, just try

apply(x, 1, fit, time)

Hope this helps,

Rui Barradas

[Michael Weylandt]

You can run multiple regressions at once:

x <- 1:4
y <- x + 10
z <- 0:3
lm(cbind(x,y) ~ z)

Michael

On Wed, May 2, 2012 at 9:48 AM, stella <[hidden email]> wrote:

> Hi,
>
> How can a function in R handle different types of input?
> I have written a function, which should calculate the slope from several
> 3-time-point measurements by linear regression
>
> 4 three-time-point-measurements:
> x<-cbind(c(1,2,3,4),c(2,3,4,5),c(3,4,5,6))
>
> time points:
> time<-c(1,3,9)
>
> function for calculating the slope by linear regression:
> fit<-function(xx,t){slope <- coefficients(lm(log(xx) ~ 0 + t))[1]
> return(slope)
> }
> alpha<-fit(x[1,],time)
>
> At the moment the function output 'alpha' is calculated for
> x(x1=1,x2=2,x3=3). I would like to get 'alphas' for all four rows of x
> without using a for-loop.  If I use 'mapply', I get outputs to very entry of
> x (12 outputs) instead of four.
>
> Thank you very much in advance! Yor help is really appreciated!
> Stella
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/How-can-a-function-in-R-handle-different-types-of-input-tp4603263.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.