Re: [R] Why does "summary" show number of NAs as non-integer?

From: Marc Schwartz <MSchwartz_at_MedAnalytics.com>
Date: Wed 01 Jun 2005 - 09:32:05 EST

On Tue, 2005-05-31 at 17:14 -0500, Earl F. Glynn wrote:
> Example:
>
> > set.seed(19)
> > summary( c(NA, runif(10,1,100), NaN) )
> Min. 1st Qu. Median Mean 3rd Qu. Max. NA's
> 7.771 24.850 43.040 43.940 63.540 83.830 2.000
>
> Why isn't the number of NA's just "2" instead of the "2.000" shown above?

>
> efg

This is actually related to the thread on formatting numbers.

In reviewing the Detail section of ?print.default:

"The same number of decimal places is used throughout a vector, This means that digits specifies the minimum number of significant digits to be used, and that at least one entry will be printed with that minimum number."

'digits' in the above is the digits argument to print.default(). In this case, it defaults to options("digits"), which is 7.

In the above output from summary, you will note that all of the output has three digits after the decimal place.

Thus:

> c(2)

[1] 2

> c(2, 3)
[1] 2 3

> c(2, 3.5)
[1] 2.0 3.5

> c(2, 3.57)
[1] 2.00 3.57

> c(2, 3.579)
[1] 2.000 3.579

Note how the output format of "2" varies depending upon how many decimal places I use in the second element.

This goes to the need to use other functions where there is a need to exert greater control over how numeric output can be formatted and aligned using formatC() and/or sprintf().

For example:

> sprintf("0 decimal places: %d 3 decimal places: %4.3f", 2, 3.57911)
[1] "0 decimal places: 2 3 decimal places: 3.579"

See ?sprintf and ?formatC for more information.

HTH, Marc Schwartz



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