Hi All,
Anyone know how to quickly query some summary information on the
components of a list?
For example, I have a list that contains dataframes (originally
generated by using split() on one large data frame).
I simply want to know the number of rows in the longest dataframe from the list.
Example, if my list has 3 data frames, and the first has 2 rows, the
second 8 rows, and the third 3 rows, I want to ask something like:
max(nrow(myList))
which would ideally return "8".
but this is obviously wrong syntax.
Currently, I'm looping through each of the data frames in the list,
searching for the max rows, but I'm sure there must be a faster way.
Thanks,
Jonatahn
Jonathan wrote:> Hi All, > Anyone know how to quickly query some summary information on the > components of a list? > > For example, I have a list that contains dataframes (originally > generated by using split() on one large data frame). > > > I simply want to know the number of rows in the longest dataframe from the list. > > Example, if my list has 3 data frames, and the first has 2 rows, the > second 8 rows, and the third 3 rows, I want to ask something like: > > > max(nrow(myList)) > which would ideally return "8". >max(sapply(myList, nrow))> > but this is obviously wrong syntax. > > Currently, I'm looping through each of the data frames in the list, > searching for the max rows, but I'm sure there must be a faster way. > > Thanks, > Jonatahn > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.
You need sapply max(sapply(myList, nrow)) Thierry ------------------------------------------------------------------------ ---- ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek team Biometrie & Kwaliteitszorg Gaverstraat 4 9500 Geraardsbergen Belgium Research Institute for Nature and Forest team Biometrics & Quality Assurance Gaverstraat 4 9500 Geraardsbergen Belgium tel. + 32 54/436 185 Thierry.Onkelinx at inbo.be www.inbo.be To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey> -----Oorspronkelijk bericht----- > Van: r-help-bounces at r-project.org > [mailto:r-help-bounces at r-project.org] Namens Jonathan > Verzonden: donderdag 19 augustus 2010 17:42 > Aan: r-help > Onderwerp: [R] Quick q. on lists > > Hi All, > Anyone know how to quickly query some summary information > on the components of a list? > > For example, I have a list that contains dataframes > (originally generated by using split() on one large data frame). > > > I simply want to know the number of rows in the longest > dataframe from the list. > > Example, if my list has 3 data frames, and the first has 2 > rows, the second 8 rows, and the third 3 rows, I want to ask > something like: > > > max(nrow(myList)) > which would ideally return "8". > > > but this is obviously wrong syntax. > > Currently, I'm looping through each of the data frames in the > list, searching for the max rows, but I'm sure there must be > a faster way. > > Thanks, > Jonatahn > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >Druk dit bericht a.u.b. niet onnodig af. Please do not print this message unnecessarily. Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver weer en binden het INBO onder geen enkel beding, zolang dit bericht niet bevestigd is door een geldig ondertekend document. The views expressed in this message and any annex are purely those of the writer and may not be regarded as stating an official position of INBO, as long as the message is not confirmed by a duly signed document.
Hi Jonathan,
Try this:
# list of data frames
mylist <- list(d1 = matrix(rnorm(100), ncol = 10),
d2 = matrix(rnorm(100), ncol = 5),
d3 = matrix(rnorm(100), ncol = 20))
# max number of rows
max(do.call(c, lapply(mylist, nrow)))
# [1] 20
HTH,
Jorge
On Thu, Aug 19, 2010 at 11:42 AM, Jonathan <> wrote:
> Hi All,
> Anyone know how to quickly query some summary information on the
> components of a list?
>
> For example, I have a list that contains dataframes (originally
> generated by using split() on one large data frame).
>
>
> I simply want to know the number of rows in the longest dataframe from the
> list.
>
> Example, if my list has 3 data frames, and the first has 2 rows, the
> second 8 rows, and the third 3 rows, I want to ask something like:
>
>
> max(nrow(myList))
> which would ideally return "8".
>
>
> but this is obviously wrong syntax.
>
> Currently, I'm looping through each of the data frames in the list,
> searching for the max rows, but I'm sure there must be a faster way.
>
> Thanks,
> Jonatahn
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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