[R-sig-eco] LEVELS function NULL

[Peter Solymos]

R >= 4.0 will treat categorical variables as character
(stringsAsFactors=FALSE is the new default) when importing via e.g.
read.table(). If you want factors, you have to make it explicit either as
Torsten showed or by setting stringsAsFactors=TRUE.

Cheers,

Peter

On Tue, Jun 23, 2020 at 10:05 AM Torsten Hauffe <torsten.hauffe using gmail.com>
wrote:

> Hi,
>
> What is the output of
> class(my_data$Sampling)?
>
> If it is not factor (but character), you could write
> my_data$Sampling <- as.factor(my_data$Sampling)
>
> Then levels(my_data$Sampling) should return Sep18 etc.
>
> Cheers!
>
> On Tue, Jun 23, 2020 at 6:00 PM Vesna Gulin <vesna.gulin using biol.pmf.hr>
> wrote:
>
> > Hi everyone,
> >
> >
> >
> > It has been a couple months now of using R and I am slowly trying to
> switch
> > from using Statistica to R in order to process my data (for PhD
> purposes).
> >
> >
> >
> > I did some basic statistics and now I would like to try Kruskal-Wallis
> > (following this guideline:
> >
> > http://www.sthda.com/english/wiki/kruskal-wallis-test-in-r )
> >
> > but I have been stuck for days as I can't seem to find a reason why the
> > levels function keeps giving me NULL.
> >
> >
> >
> > My data is a data frame:
> >
> >
> >
> > my_data
> >
> >    Temperature Sampling
> >
> > 1         9.90    Dec17
> >
> > 2        10.00    Dec17
> >
> > 3        10.00    Dec17
> >
> > 4        10.10    Dec17
> >
> > 5         9.90    Dec17
> >
> > 6        10.10    Dec17
> >
> > 7        10.20    Dec17
> >
> > 8        10.10    Jan18
> >
> > 9        10.50    Jan18
> >
> > 10       10.80    Jan18
> >
> > 11       10.30    Jan18
> >
> > 12       10.30    Jan18
> >
> > 13       10.20    Jan18
> >
> > 14       10.50    Jan18
> >
> > 15       20.90    Jun18
> >
> > 16       20.80    Jun18
> >
> > 17       20.50    Jun18
> >
> > 18       20.50    Jun18
> >
> > 19       20.70    Jun18
> >
> > 20       20.60    Jun18
> >
> > 21       20.50    Jun18
> >
> > 22       10.50    Mar18
> >
> > 23       11.40    Mar18
> >
> > 24       10.90    Mar18
> >
> > 25       10.60    Mar18
> >
> > 26       11.60    Mar18
> >
> > 27       11.20    Mar18
> >
> > 28       12.20    Mar18
> >
> > 29       19.40    May18
> >
> > 30       19.00    May18
> >
> > 31       20.80    May18
> >
> > 32       19.50    May18
> >
> > 33       18.60    May18
> >
> > 34       18.10    May18
> >
> > 35       19.20    May18
> >
> > 36       16.80    Nov18
> >
> > 37       16.50    Nov18
> >
> > 38       18.40    Nov18
> >
> > 39       18.10    Nov18
> >
> > 40       16.70    Nov18
> >
> > 41       16.70    Nov18
> >
> > 42       18.50    Nov18
> >
> > 43       15.50    Oct17
> >
> > 44       15.10    Oct17
> >
> > 45       15.00    Oct17
> >
> > 46       15.80    Oct17
> >
> > 47       15.20    Oct17
> >
> > 48       15.10    Oct17
> >
> > 49       15.20    Oct17
> >
> > 50       23.40    Sep18
> >
> > 51       24.05    Sep18
> >
> > 52       23.70    Sep18
> >
> > 53       23.40    Sep18
> >
> > 54       24.05    Sep18
> >
> > 55       23.80    Sep18
> >
> > 56       24.15    Sep18
> >
> >
> >
> > When I hit levels(my_data$Sampling) it gives me
> > NULL
> >
> >
> >
> > I would very much appreciate any help.
> >
> >
> >
> > Kind regards,
> >
> > Vesna
> >
> >
> >
> >
> >
> >
> >
> > Vesna Gulin,  Research Assistant
> >
> >
> >
> > Department of Biology
> >
> >
> >
> > Faculty of Science
> >
> > University of Zagreb
> >
> >
> >
> > Rooseveltov trg 6, 10000 Zagreb, Croatia
> >
> >
> >
> >
> >         [[alternative HTML version deleted]]
> >
> > _______________________________________________
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> > R-sig-ecology using r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
> >
>
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>
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-- 
Péter Sólymos, PhD
Senior Statistical Ecologist
solymos using ualberta.ca 780-492-8534
Alberta Biodiversity Monitoring Institute http://www.abmi.ca
Boreal Avian Modelling Project http://www.borealbirds.ca

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