R help - May 2012 - How can a function in R handle different types of input?

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
 


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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


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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 <dorotheabusse at yahoo.de>
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.
>
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