Dear Hervé,
This is indeed a wise recommendation; I hadn't thought about colnames()
vs. names(), and in general 2D vs. list notations.
I will have to edit a bit more than I thought.
Thank you all for all these hints!
Best,
Ivan
--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and
Hi Ivan,
On 3/31/20 06:44, Ivan Calandra wrote:
That's exactly why I was asking if it really is equivalent and if there
are issues using one function or the other
Not that I know. It's mostly a matter of taste and code readability.
Either use the 2D interface:
ncol(df), colnames(df), df[
Thank you Greg for the insights!
I agree with you that the decrease in speed is not worth the decrease in
readability, and I'll change my length() calls to ncol().
Best,
Ivan
--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research
As others have pointed out, ncol calls the length function, so you are
pretty safe in terms of output of getting the same result when applied
to the results of functions like read.csv (there will be a big
difference if you ever apply those functions to a matrix or some other
data structures).
One
Hi Ivan,
Like Ivan Krylov, I'm not aware of circumstances for simple dataframes
where ncol(DF) does not equal length(DF).
As I understand it, using ncol() versus length() is important when
you're examining an object returned from a function like sapply(),
since sapply() will simplify one-column
Thanks Matthias for the details!
Ivan
--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
56567 Neuwied, Germany
+49 (0) 2631 9772-243
should have added: dim(x)[2L] -> length(x)
Am 31.03.20 um 16:21 schrieb Prof. Dr. Matthias Kohl:
Dear Ivan,
if I enter ncol in the console, I get
function (x)
dim(x)[2L]
indicating that function dim is called. Function dim has a method for
data.frame; see methods("dim").
The dim-method
Dear Ivan,
if I enter ncol in the console, I get
function (x)
dim(x)[2L]
indicating that function dim is called. Function dim has a method for
data.frame; see methods("dim").
The dim-method for data.frame is
dim.data.frame
function (x)
c(.row_names_info(x, 2L), length(x))
Hence, it
Thanks Ivan for the answer.
So it confirms my first thought that these two functions are equivalent
when applied to a "simple" data.frame.
The reason I was asking is because I have gotten used to use length() in
my scripts. It works perfectly and I understand it easily. But to be
honest, ncol()
On Tue, 31 Mar 2020 14:47:54 +0200
Ivan Calandra wrote:
> On a simple data.frame (i.e. each element is a vector), ncol() and
> length() will give the same result.
> Are they just equivalent on such objects, or are they differences in
> some cases?
I am not aware of any exceptions to
That's exactly why I was asking if it really is equivalent and if there
are issues using one function or the other
--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
Yes it does because length(list) gives you the number of elements of the
list. And in the case of a data frame object that is the number of columns,
or ncol().
On Tue, Mar 31, 2020 at 4:37 PM Ivan Calandra wrote:
> Thanks Eric,
>
> I know that, but that doesn't really answer my question, does
Thanks Eric,
I know that, but that doesn't really answer my question, does it?
Ivan
--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
56567 Neuwied, Germany
+49
A data frame is a special case of a list. It is a list of its columns.
> is.list( your_data_frame )
# TRUE
On Tue, Mar 31, 2020 at 4:04 PM Ivan Calandra wrote:
> Dear useRs,
>
> I have a very simple question:
> On a simple data.frame (i.e. each element is a vector), ncol() and
> length()
Dear useRs,
I have a very simple question:
On a simple data.frame (i.e. each element is a vector), ncol() and
length() will give the same result.
Are they just equivalent on such objects, or are they differences in
some cases?
Is one of them to be preferred for whatever reason?
Thanks you,
Ivan
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