R help - Oct 2008 - lars

I am trying to use the lars package in R to carry out lasso analysis.
However, I am having some problems.  Please could you help me with the
following questions:

1) Exactly what format do x and y need to be in for cv.lars(x, y) and lars
(x, y)?  And what information do x and y need to contain exactly?  I have
tried using to test just a simple matrix of numeric values for x and a
simple vector of numeric values for y but have got error messages.

2)For the K-fold cross-validation are the K subsets randomly chosen?

I have read the document 'The lars Package', which is helpful.  However,
when I try using the package I am getting a variety of error messages.

I am not an advanced user of R so please do be very specific.

Thanks in advance for your help in this matter.

Hi,

Can anyone tell me how we can have the optimal value of "lambda" from
lars
package? I want to extract the estimates against this optimal value of
"lambda". I have tried the predict.lars and coef.lars but these
provide
entire sequence of coefficients. I don't know how to have the optimal one.

Cheers,

-- 
Sohail Chand

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