R4DS 2e; Chapter 17, Section 17.3.3 - Modifying components

[mikael-k-b]

I am learning R, and I have found r4ds to be invaluable, many thanks!
In Section 17.3.3 Modifying components, you wrote: "...Alternatively, rather than modifying an existing variable, you can create a new date-time with update(). This also allows you to set multiple values in one step:...".
I however have been unable to create new variables this way, but get an error message; "...Error: object 'variable_name' not found...".
If this isn't an issue and I have misunderstood something, apologies.

Many thanks,
Mikael_k_b