matplot((-4:5)^2, main = "Quadratic") # almost identical to plot(*) 
     sines <- outer(1:20, 1:4, function(x, y) sin(x / 20 * pi * y)) 
     matplot(sines, pch = 1:4, type = "o", col = rainbow(ncol(sines))) 
 
     x <- 0:50/50 
     matplot(x, outer(x, 1:8, function(x, k) sin(k*pi * x)), 
             ylim = c(-2,2), type = "plobcsSh", 
             main= "matplot(,type = \"plobcsSh\" )") 
     ## pch & type =  vector of 1-chars : 
     matplot(x, outer(x, 1:4, function(x, k) sin(k*pi * x)), 
             pch = letters[1:4], type = c("b","p","o")) 
 
     data(iris)                  # is data.frame with  `Species' factor 
     table(iris$Species) 
     iS <- iris$Species == "setosa" 
     iV <- iris$Species == "versicolor" 
     op <- par(bg = "bisque") 
     matplot(c(1, 8), c(0, 4.5), type= "n", xlab = "Length", ylab = "Width", 
             main = "Petal and Sepal Dimensions in Iris Blossoms") 
     matpoints(iris[iS,c(1,3)], iris[iS,c(2,4)], pch = "sS", col = c(2,4)) 
     matpoints(iris[iV,c(1,3)], iris[iV,c(2,4)], pch = "vV", col = c(2,4)) 
     legend(1, 4, c("    Setosa Petals", "    Setosa Sepals", 
                    "Versicolor Petals", "Versicolor Sepals"), 
            pch = "sSvV", col = rep(c(2,4), 2)) 
 
     nam.var <- colnames(iris)[-5] 
     nam.spec <- as.character(iris[1+50*0:2, "Species"]) 
     iris.S <- array(NA, dim = c(50,4,3), dimnames = list(NULL, nam.var, nam.spec)) 
     for(i in 1:3) iris.S[,,i] <- data.matrix(iris[1:50+50*(i-1), -5]) 
 
     matplot(iris.S[,"Petal.Length",], iris.S[,"Petal.Width",], pch="SCV", 
             col = rainbow(3, start = .8, end = .1), 
             sub = paste(c("S", "C", "V"), dimnames(iris.S)[[3]], 
                         sep = "=", collapse= ",  "), 
             main = "Fisher's Iris Data")