R is basically following some basic configuration settings for printing the number of required digits. You can change this with the digits
option as follows:
> options(digits=9)
> y <- as.character("0.912345678")
> as.numeric(y)
[1] 0.912345678
Small EDIT for clarity:
digits
corresponds to the number of digits to display in total, and not just the number of digits after the comma.
For example,
> options(digits=9)
> y <- as.character("10.123456789")
> as.numeric(y)
[1] 10.1234568
In your example above the leading zero before the comma is not counted, this is why 9 digits was enough to display the complete number.
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