Hi, The resulting matrix will be *really* large, so make sure you have enough RAM. You might reduce this by dropping all the levels of the factor that have zero counts. As far as the solution, it is a one-liner, but not really a crypic one:
model.matrix(~foo-1) (assuming that you haven't changed the default contrasts in options() ) > Hi Helpers: > > I have a factor object that has 314k entries of 39 land cover types. > (This object can be coerced to characters neatly should that be easier > to work with.) > > length(foo) > [1] 314482 > > foo[1:10] > [1] Montane Chaparral Barren Red Fir Red Fir > > [5] Red Fir Red Fir Red Fir Red Fir > > [9] Red Fir Red Fir > 39 Levels: Alpine-Dwarf Shrub Annual Grassland Aspen Barren ... White > Fir > > summary(foo) > Alpine-Dwarf Shrub Annual Grassland > Aspen > 7402 0 > 582 > Barren Bitterbrush Blue > Oak-Foothill Pine > 69111 9 > 0 > Blue Oak Woodland Chamise-Redshank Chaparral Closed-Cone > Pine-Cypress > 0 0 > 0 > Cropland Desert Scrub > Douglas-Fir > 0 0 > 0 > Eastside Pine Freshwater Emergent Wetland > Jeffrey Pine > 0 0 > 11342 > Joshua Tree Juniper > Lacustrine > 0 1293 > 501 > Lodgepole Pine Low Sage > Mixed Chaparral > 60332 31 > 1043 > Montane Chaparral Montane Hardwood Montane > Hardwood-Conifer > 6648 326 > 0 > Montane Riparian Orchard and Vineyard > Perennial Grassland > 180 0 > 17 > Pinyon-Juniper Ponderosa Pine > Red Fir > 968 708 > 66263 > Riverine Sagebrush Sierran > Mixed Conifer > 0 2292 > 14264 > Subalpine Conifer Urban > Valley-Foothill Riparian > 66237 0 > 0 > Valley Oak Woodland Wet Meadow > White Fir > 0 2216 > 2717 > > > > > I want to make a matrix that has the cover types as columns and > length(foo) rows. I want the matrix entities to be scored one if that > cover type else zero. > > foo.mat <- matrix(data = 0, nrow = length(foo), > ncol = nlevels(foo)) > > colnames(foo.mat) <- levels(foo) > > That is easy enough but I'm at a loss as how to populate it properly. > > In case I'm not being clear. This is what I want: > > > foo[1] > [1] Montane Chaparral > 39 Levels: Alpine-Dwarf Shrub Annual Grassland Aspen Barren ... White > Fir > > foo.mat[1,] J.R. Lockwood 412-683-2300 x4941 [EMAIL PROTECTED] http://www.rand.org/methodology/stat/members/lockwood/ ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
