[R] Lattice scales question: using "at" when log = TRUE

[Afshartous, David]

All,

I have a simple lattice plot where I have set log = TRUE for the y scale.

When I attempt to change the tick locations via the "at" argument within
scales, the supplied numeric vector is not followed. Any suggestions much
appreciated for the example below:

y = c(10^1.5, 10^2, 10^3, 10^2)
t = c(1,2,3,4)
xyplot(y ~ t, type = "b", scales = list(y = list(log = TRUE)))

## tick marks not followed for supplied marks below:
xyplot(y ~ t, type = "b", scales = list(y = list(log = TRUE), at = c(10^1,
10^2, 10^2.5, 10^3)))

Cheers,
David

PS - 
Another thing is that the scale is no longer in scientific notations, but
that is okay since this can be fixed via the labels argument within scales:
e.g., labels = c(expression(10^1), expression(10^2), ...)
An example of fancy labels for log axes is on p.147 of Deepayan's Lattice
book.