[R-sig-Geo] problem with enveloped test in spatstat

Marcelino de la Cruz Rot marcelino.delacruz at urjc.es
Sat Apr 21 23:50:32 CEST 2018


Hi David,

This is very clearly explained in page 393 of Baddeley et al. 2015.

Basically, the MAD test is affected by transformations of the summary 
function, with the L-function providing more powerful tests because of 
its stabilization of the variance.

If you are interested in point pattern analysis I would recommend you to 
get a copy of this nice book.


Cheers,

Marcelino


Adrian Baddeley, Ege Rubak, Rolf Turner (2015). Spatial Point Patterns: 
Methodology and Applications with R. London: Chapman and
   Hall/CRC Press.
http://www.crcpress.com/Spatial-Point-Patterns-Methodology-and-Applications-with-R/Baddeley-Rubak-Turner/9781482210200/ 







El 21/04/2018 a las 18:05, David Unwin escribió:
> Can any *spatstat* user explain to me why the two p-values obtained below
> for an envelope test against CSR are so different?
>
>
>
>> data(swedishpines)
>> d<-swedishpines
>> plot(d)
>> mad.test(d,Kest,nsim=999,verbose=F)
>
>
>          Maximum absolute deviation test of CSR
>
>          Monte Carlo test based on 999 simulations
>
>          Summary function: K(r)
>
>          Reference function: theoretical
>
>          Alternative: two.sided
>
>          Interval of distance values: [0, 24] units (one unit = 0.1 metres)
>
>          Test statistic: Maximum absolute deviation
>
>          Deviation = observed minus theoretical
>
>
>
> data:  d
>
> mad = 150.69, rank = 216, p-value = *0.216*
>
>
>
>> mad.test(d,*Lest*,nsim=999,verbose=F)
>
>
>          Maximum absolute deviation test of CSR
>
>          Monte Carlo test based on 999 simulations
>
>          Summary function: L(r)
>
>          Reference function: theoretical
>
>          Alternative: two.sided
>
>          Interval of distance values: [0, 24] units (one unit = 0.1 metres)
>
>          Test statistic: Maximum absolute deviation
>
>          Deviation = observed minus theoretical
>
>
>
> data:  d
>
> mad = 2.9921, rank = 9, p-value = *0.009*
>
>
>
> *!!!*
>
>
>
> These data are dispersed relative to CSR:
>
>> kl<-envelope(d,Kest,nsim=999,correction="border")
>> plot(kl)
>
> Dave Unwin
>
> 	[[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> .
>

-- 
Marcelino de la Cruz Rot
Depto. de Biología y Geología
Física y Química Inorgánica
Universidad Rey Juan Carlos
Móstoles España



More information about the R-sig-Geo mailing list