On 14/05/2010 5:35 AM, (Ted Harding) wrote:
On 13-May-10 23:43:58, yjmha69 wrote:
Hi there,
library(faraway)
pima
pregnant glucose diastolic triceps insulin bmi diabetes age test
1 6 148 72 35 0 33.6 0.627 50 1
2 1 85 66 29 0 26.6 0.351 31 0
data(pima)
pima
pregnant glucose diastolic triceps insulin bmi diabetes age test
1 6 148 72 35 0 33.6 0.627 50 1
2 1 85 66 29 0 26.6 0.351 31 0
As you can see, I can already use pima without running data(pima),
after running data(pima), it looks the same. So what's the reason to
use data(pima) ?
Thanks
YJM
The difference is that data(pima) will load the dataset pima
(which can be found in the package "faraway") without the use
of library(faraway). It won't load anything else from faraway.
That won't work. Unless you attach faraway, R won't know what "pima"
refers to, and will just give an error.
The difference between data(pima) and pima is that, in this case, there
isn't really much of one, but in other cases there might be. Prior to
the introduction of lazy loading of data, it always made a difference:
the pima object wouldn't be loaded into memory until requested by
data(pima). With lazy loading, a stub for the object is always in
memory, with the main part of the object only loaded on first use. Many
packages (including faraway) use lazy loading of data so data() is to
some extent unnecessary: but there are some circumstances under which
lazy loading won't work, so a few packages don't use it, and I believe
it is not the default.
Duncan Murdoch
When you use library(faraway) you will load everything in the
package faraway, including of course the dataset pima (which is
why you see no difference, since that dataset is the same whichever
way you load it).
So with data() you put less load on your system, and also avoid
possible conflicts between what you already have in your environment
and what would be brought in when you do library(faraway).
Ted.
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E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk>
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Date: 14-May-10 Time: 10:35:15
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