[R] How to use a matrix in pcurve?

[XP Sun]

Hi, Everyone,

I want to calculate the principal curve of a points set.
First I read the points'coordinate with function "scan", 
then converted it to matrix with the function "matrix",
and fit the curve with function "principal.curve".

Here is my data in the file "bmn007.data": 
0.023603	 -0.086540	 -0.001533
0.024349	 -0.083877	 -0.001454
..
..
0.025004	 -0.083690	 -0.001829
0.025562	 -0.083877	 -0.001857
0.026100	 -0.083877	 0.000090
0.025965	 -0.083877	 0.002574

and the code as follow:

pp <- scan("bmn007.data", quiet= TRUE)
x <- matrix(pp, nc=2, byrow=TRUE)
fit <- principal.curve(x, plot = TRUE)
points(fit,col="red")

By now, I got a right result. 
But when i changed to use pcurve with matrix x as "pcurve(x)",
an error was thrown as following:

Estimating starting configuration using : CA
Error in h %*% diag(sqrt(d)) : non-conformable arguments

How to convert a matrix to the format could be accepted by "pcurve"?
Any help appreciated!

Regards
- Sun