Hi,
I am checking for spatial autocorrelation in my dataset. It comprises the ID of the nests, the longitude and latitude for each of the nest boxes and the number of fledged chicks for each nest box. I want to know if reproductive success is spatially autocorrelated in our bird colony.
For this, I computed the distance matrix for nest boxes to know the distance between each nest box and the rest of nest boxes. Following this, I designed distance bands (distance lags) to calculate Moran's I for each lag specifically. As I have multiple data for several years (2014-2020), I wonder if there is any way to get a mean Moran's Index of all the years, instead of calculating an index for each year.
It is my first time doing these types of analysis so any advice would be very much appreciated!!
Thank you.
Iraida
Since you use the same study area each year, Moran values are comparable, so you can calculate a mean value across years, but also calculate for individual years to observe variation. Other than that, there are no rules :)
Hi Iraida, how are you? I asked one friend and he told me this:
Hi Iraida, I performed a similar analysis in my PhD, but using the number of soil mites across sites over time. I am not aware of any coefficient of spatial autocorrelation that incorporates temporal variation, even though this is theoretically possible (e.g. one can use Moran's I on a time series by setting one of the dimensions to a constant). For a spatiotemporal coefficient, one would have to add another dimension to Moran's I formula. What people generally do in this situation is to average the variable rather than the coefficient, i.e. apply Moran's I to the average number of fledged chicks over time. Yet, it is always possible that the spatial autocorrelation pattern changes over time, so it may be informative to have separate correlograms. Also, notice that you don't need to break distances into bands; one can estimate spatial autocoorrelation as a continuous function of distance by using spline correlograms (e.g. package "ncf" in R). Best wishes, Pedro
Andrew Paul McKenzie Pegman Thank you so much for your answer!! :-) I think I would be following your advice and keep years separated and then a mean :-)
Thiago Bicudo Krempel Santana Thiago!! How are you? Thank you so much for reaching out and for the help of your friend :-)
I have been looking at the spline correlograms and I think I am not completely able to interpret the x axis on the correlogram, which is the unit?
This is the code that I wrote and then I got the graph I attached at this message (no signs of spatial correlation):
sc
Hey, Iraida Redondo García sorry for the delay.
I think that the unit will depend on which unit is the coordinate, no? If it's decimal degrees, then the distance is in decimal degrees.
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