add R sample function and readme

Signed-off-by: Chanyub Park <mrchypark@gmail.com>

sample-functions/BaseFunctions/R/Dockerfile

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+FROM artemklevtsov/r-alpine:latest
+
+ADD https://github.com/alexellis/faas/releases/download/0.6.1/fwatchdog /usr/bin
+RUN chmod +x /usr/bin/fwatchdog
+
+WORKDIR /root/
+
+COPY handler.R .
+
+ENV fprocess="Rscript handler.R"
+
+HEALTHCHECK --interval=1s CMD [ -e /tmp/.lock ] || exit 1
+
+CMD ["fwatchdog"]
+

sample-functions/BaseFunctions/R/README.Rmd

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+---
+title: "BaseFunction for R"
+output: github_document
+---
+
+```{r setup, include=FALSE}
+knitr::opts_chunk$set(echo = TRUE)
+```
+
+Use this FaaS function using R.
+
+**Deploy the base R function**
+
+(Make sure you have already deployed FaaS with ./deploy_stack.sh in the root of this Github repository.
+
+* Option 1 - click *Create a new function* on the FaaS UI
+
+* Option 2 - use the [faas-cli](https://github.com/alexellis/faas-cli/) (experimental)
+
+```
+# curl -sSL https://get.openfaas.com | sudo sh
+
+# faas-cli -action=deploy -image=functions/base:R-3.4.1-alpine -name=baser
+200 OK
+URL: http://localhost:8080/function/baser
+```
+
+**Say Hi with input**
+
+`curl` is good to test function.
+
+```
+$ curl http://localhost:8080/function/baser -d "test"
+```
+
+**Customize the transformation**
+
+If you want to customise the transformation then edit the Dockerfile or the fprocess variable and create a new function.
+
+**Remove the function**
+
+You can remove the function with `docker service rm baser`.

sample-functions/BaseFunctions/R/README.md

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+BaseFunction for R
+================
+
+Use this FaaS function using R.
+
+**Deploy the base R function**
+
+(Make sure you have already deployed FaaS with ./deploy\_stack.sh in the root of this Github repository.
+
+-   Option 1 - click *Create a new function* on the FaaS UI
+
+-   Option 2 - use the [faas-cli](https://github.com/alexellis/faas-cli/) (experimental)
+
+<!-- -->
+
+    # curl -sSL https://get.openfaas.com | sudo sh
+
+    # faas-cli -action=deploy -image=functions/base:R-3.4.1-alpine -name=baser
+    200 OK
+    URL: http://localhost:8080/function/baser
+
+**Say Hi with input**
+
+`curl` is good to test function.
+
+    $ curl http://localhost:8080/function/baser -d "test"
+
+**Customize the transformation**
+
+If you want to customise the transformation then edit the Dockerfile or the fprocess variable and create a new function.
+
+**Remove the function**
+
+You can remove the function with `docker service rm baser`.

sample-functions/BaseFunctions/R/build.sh

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+#!/bin/sh
+
+echo "Building functions/base:R-3.4.1-alpine"
+docker build -t functions/base:R-3.4.1-alpine .
+

sample-functions/BaseFunctions/R/handler.R

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+#!/usr/bin/env Rscript
+
+f <- file("stdin")
+open(f)
+line<-readLines(f, n=1, warn = FALSE)
+
+write(paste0("Hi ", line), stderr())