[R] copula

[Dominique Katshunga]

Dear R-helper,
Is there any thing that I am doing wrong in the following codes:
> norm.cop <- normalCopula(0.5)
> persp(norm.cop, dcopula)
The last command produces what follows

Error in persp(x, y, z, xlim, ylim, zlim, theta, phi, r, d, scale,
expand,  : 
        invalid 'x' argument
In addition: Warning messages:
1: no non-missing arguments to min; returning Inf 
2: no non-missing arguments to max; returning -Inf 
3: no non-missing arguments to min; returning Inf 
4: no non-missing arguments to max; returning -Inf 
5: is.na() applied to non-(list or vector) in: is.na(x) 
6: no non-missing arguments to min; returning Inf 
7: no non-missing arguments to max; returning -Inf
I remember that I tried the same two commands exactly the way they
appear above and I had the surface drawn properly. Does anyone have an
idea what this could possibly mean? 
thanks,
Dominique