I can't figure out why this is returning an NA for the slope in one case,
but not in the other.

I can tell that R thinks the first case is singular, but why isn't the
second?

## Define X and Y
## There are two versions of x
##     1) "as is"
##     2) shifted to start at 0
y  = c(58, 57, 57, 279, 252, 851, 45, 87, 47)
x1 = c(1334009411.437, 1334009411.437, 1334009411.437, 1334009469.297,
        1334009469.297, 1334009469.297, 1334009485.697, 1334009485.697,
1334009485.697)
x2 = x1 - min(x1)

## Why doesn't the LM model work for the "as is" x?
lm(y~x1)
lm(y~x2)


My environment:
Windows XP,
R 2.14.1

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