To compile Rmd files to PDF with a Makefile

Makefile

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+#!/usr/bin/env make
+
+%.pdf: %.Rmd
+	@R --quiet --file=make.R --args $<

make.R

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+#!/usr/bin/env R
+
+# Render R markdown to PDF.
+# Invoke with:
+# > R -q -f make.R --args my_report.Rmd
+
+# load packages
+require(rmarkdown)
+
+# require a parameter naming file to render
+if (length(args) == 0) {
+    stop("Error: missing file operand", call. = TRUE)
+} else {
+    # read report to render from command line
+    for (rmd in commandArgs(trailingOnly = TRUE)) {
+        # render Rmd to PDF
+        if ( grepl("\\.Rmd$", rmd) && file.exists(rmd)) {
+            render(rmd, pdf_document())
+        } else {
+            print(paste("Ignoring: ", rmd))
+        }
+    }
+}