Usage
panel.radarplot(x, y, groups = NULL, pch = if (is.null(groups)) plot.symbol$pch else superpose.symbol$pch, col, col.line = if (is.null(groups)) plot.line$col else superpose.line$col, col.symbol = if (is.null(groups)) plot.symbol$col else superpose.symbol$col, font = if (is.null(groups)) plot.symbol$font else superpose.symbol$font, fontfamily = (if (is.null(groups)) plot.symbol else superpose.symbol)$fontfamily, fontface = (if (is.null(groups)) plot.symbol else superpose.symbol)$fontface, lty = if (is.null(groups)) plot.line$lty else superpose.line$lty, cex = if (is.null(groups)) plot.symbol$cex else superpose.symbol$cex, fill = if (is.null(groups)) plot.symbol$fill else superpose.symbol$fill, lwd = if (is.null(groups)) plot.line$lwd else superpose.line$lwd, w = 0.12, h = 0.06, strength = NULL, ...)