R help - Jan 2013 - D_f_norm function

Hi every body,
i am using D_f_norm function from library stat in R
i am using it to find the standard deviation of the output of a function
'calculate_Z0' that has one of it is inputs as a random variable
'W' , with a standard deviation 'Sigm3LER', when i change the
mean of this random variable 'Width', i expected the standard deviation
output from d_f_norm to change respectively.
here is the code i use



Z0_extra <- function(W, Thickness,Height,Spacing)
{
 f <- function(vec) { calculate_Z0(vec[1],Thickness, Height,Spacing) }
 tmp <- D_f_norm(f, means=c(Width), sds=c(Sigm3LER))
 list(mean=tmp$mean ,sd=tmp$sd )
}

calculate_Z0 <- function(W,Thickness, Height, Spacing)
{
Z0 
<- sqrt((Resistivity/(Thickness * 
W))/(2*3.14*5*10^9*(epsilon*(1.15*(W/Height) + 2.8* 
(Thickness/Height)^0.222 + 2*( 
0.03*(W/Height)+0.83*(Thickness/Height)-.07*(Thickness/Height)^0.222)*(Spacing/Height)^
 (-1.34)) )))
}

but this does not happen, although i change the mean of the output
"Width", the standard deviation of the output function
'Z0_extra' does not change.
i do not no if this the correct output and i have to change my expectations or
there is something wrong in the way i use D_f_norm.

can any one advise me on that?

thanks and best regards
Eman


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