[R] 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
 


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