| mackp {gamair} | R Documentation |
This data frame provides a regular grid of values of some predictor variables useful for modelling mackerel egg abundances. Its main purpose is to enable mackerel egg densities to be predicted over a regular spatial grid within the area covered by the 1992 mackerel egg survey (see mack), using a fitted generalised additive model.
data(mackp)
A data frame with 5 columns. Each row corresponds to one spatial location within the survey area. The columns are as follows:
lonLongitude of the gridpoint in degrees east
latLatitude of the gridpoint in degrees north.
b.depthThe sea bed depth at the gridpoint.
c.distThe distance from the gridpoint to the 200m sea bed depth contour.
salinitySalinity interpolated onto the grid (from mack measurements).
temp.surfSurface temperature interpolated onto grid (from mack data).
temp.20mTemperature at 20m interpolated from mack data.
area.index An indexing vector that enables straightforward copying of
the other variables into a matrix suitable for plotting against longitude and
lattitude using image(). See the example below.
The grid is defined on a series of 1/4 degree lon-lat squares.
Borchers, D.L., S.T. Buckland, I.G. Priede and S. Ahmadi (1997) "Improving the precision of the daily egg production method using generalized additive models". Can. J. Fish. Aquat. Sci. 54:2727-2742.
## example of how to use `area.index' to paste gridded info. ## into a square grid (of NA's) for plotting data(mackp) lon<-seq(-15,-1,1/4);lat<-seq(44,58,1/4) zz<-array(NA,57*57) zz[mackp$area.index]<-mackp$b.depth image(lon,lat,matrix(zz,57,57))