
Last chance! 50% off unlimited learning
Sale ends in
Direct gradient analysis is a graphical representation of the abundance distribution of (typically) species along opposing environmental gradients
dga(z,x,y,step=50,pres="+",abs="-",labcex=1,
xlab = deparse(substitute(x)), ylab = deparse(substitute(y)),
pch = 1, title = "", ...)
a graph of the distribution of the z variable on a grid of x and y is displayed on the current active device.
the variable (typically a species abundance) to be plotted
the variable to use as the x axis
the variable to use as the y axis
controls the grid density fed to the GAM surface fitter
the symbol to print when a species is present (presence/absence mode)
the symbol to print when a species is absent (presence/absence mode)
the character size for contour labels
the x axis legend
the y axis legend
the symbol to print in continuous abundance plots
the title to print
miscellaneous arguments to pass to par
David W. Roberts droberts@montana.edu http://ecology.msu.montana.edu/droberts/droberts.html
‘dga’ interpolates a grid of x,y values from the supplied data
and fits a GAM (from mgcv
) of the z variable to the grid.
For presence/absence data (enterd as a logical) it employs a binomial family, for
species abundances a negative binomial is employed.
The GAM surface is then represented by a contour map and abundance
symbols as described above.
data(bryceveg) # returns a data.frame called bryceveg
x <- c(0.2,0.5,1.0,2.0,3.0,4.0,5.0,6.0)
y <- c(0.2,0.5,3.0,15.0,37.5,62.5,85.0,97.5)
cover <- abundtrans(bryceveg,x,y)
data(brycesite)
dga(round(cover$arcpat),brycesite$elev,brycesite$av)
Run the code above in your browser using DataLab