Initial commit.

.emacs.d/elpa/ess-20160208.453/etc/pkg1/R/D1tr.R

@@ -0,0 +1,20 @@
+D1tr <- function(y, x = 1)
+{
+    ## Purpose:  discrete trivial estimate of 1st derivative.
+    ## ----------------------------------------------------------------------
+    ## Arguments: x is optional; let's say we don't like "'"
+    ## ----------------------------------------------------------------------
+    ## Author: Martin Maechler, ~ 1990
+    n <- length(y)
+
+    if(length(x) == 1)
+        c(y[2] - y[1], 0.5 * (y[-(1:2)] - y[-((n-1):n)]), y[n] - y[n-1])/x
+    else {
+        ## Here, already using non-matching apostrophes, but developer mode
+        ## still seems to work ..
+        if(n != length(x)) stop("lengths' of x & 'y' must equal")
+        if(is.unsorted(x)) stop("'x' must be sorted !")
+        c(y[2] - y[1], 0.5 * (y[-(1:2)] - y[-((n-1):n)]), y[n] - y[n-1]) /
+            c(x[2] - x[1], 0.5 * (x[-(1:2)] - x[-((n-1):n)]), x[n] - x[n-1])
+    }
+}