Hi Diviya,

Take a look at the lrtest function in the lmtest package:

install.packages('lmtest)
require(lmtest)
?lrtest

HTH,
Jorge


On Sun, Jun 12, 2011 at 1:16 PM, Diviya Smith <> wrote:

> Hello there,
>
> I want to perform a likelihood ratio test to check if a single exponential
> or a sum of 2 exponentials provides the best fit to my data. I am new to R
> programming and I am not sure if there is a direct function for doing this
> and whats the best way to go about it?
>
> #data
> x <- c(1 ,10,  20,  30,  40,  50,  60,  70,  80,  90, 100)
> y <- c(0.033823,  0.014779,  0.004698,  0.001584, -0.002017, -0.003436,
> -0.000006, -0.004626, -0.004626, -0.004626, -0.004626)
>
> data <- data.frame(x,y)
>
> Specifically, I would like to test if the model1 or model2 provides the
> best
> fit to the data-
> model 1: y = a*exp(-m*x) + c
> model 2: y = a*exp(-(m1+m2)*x) + c
>
> Likelihood ratio test = L(data| model1)/ L(data | model2)
>
> Any help would be most appreciated. Thanks in advance.
>
> Diviya
>
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>
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