Add example 10.7

ch10.r

@@ -28,3 +28,35 @@ for (i in 1:20) {
 matplot(t, x, lwd=2, col="gray")
 grid()
 lines(t, 0*cos(2*pi*t), lwd=4, col="darkred")
+
+## Example 10.8
+
+# R code for Example 10.7
+x = matrix(0, 21, 20)
+t = 0:20
+
+for (i in 1:20) {
+    x[,i] = runif(1) ^ t
+}
+
+stem <- function(x,y,pch=1,...){
+    if (missing(y)){
+        y = x
+        x = 1:length(x) 
+    }
+    for (i in 1:length(x)){
+        lines(c(x[i],x[i]), c(0,y[i]), ...)
+    }
+    lines(c(x[1]-2,x[length(x)]+2), c(0,0), ...)
+}
+
+matplot(t, x, pch=1, col="gray", lwd=2)
+grid()
+
+for (i in 1:ncol(x)) {
+    stem(t, x[,i], col="gray", lwd=2)
+}
+stem(t, 1/(t+1), col="darkred", lwd=2, pch=1, type="o")
+
+
+