Update R version documentation
MODIFY
docs/source/config_files.rst
docs/source/config_files.rst
@@ -212,7 +212,7 @@ If you only need to run things once during the build phase use :ref:`postBuild`.
Sometimes you want to specify the version of the runtime
(e.g. the version of Python or R),
-but the environment specification format don't let you specify this information
+but the environment specification format will not let you specify this information
(e.g. requirements.txt or install.R).
For these cases, we have a special file, ``runtime.txt``.
@@ -220,7 +220,7 @@ For these cases, we have a special file, ``runtime.txt``.
``runtime.txt`` is only supported when used with environment specifications
that do not already support specifying the runtime
- (e.g. when using ``environment.yml`` for conda or ``Project.toml`` for Julia,
+ (when using ``environment.yml`` for conda or ``Project.toml`` for Julia,
``runtime.txt`` will be ignored).
To use python-2.7: add ``python-2.7`` in runtime.txt file.
@@ -231,8 +231,11 @@ Python 2 installed. To see a full example repository, visit our
repo2docker uses R libraries pinned to a specific snapshot on
`MRAN <https://mran.microsoft.com/documents/rro/reproducibility>`_.
You need to have a ``runtime.txt`` file that is formatted as
-``r-<YYYY>-<MM>-<DD>``, where YYYY-MM-DD is a snapshot at MRAN that will be
-used for installing libraries.
+``r-<RVERSION>-<YYYY>-<MM>-<DD>``, where YYYY-MM-DD is a snapshot at MRAN that will be
+used for installing libraries. You can set RVERSION to 3.4, 3.5 or 3.6 to select
+the version of R you want to use. If you do not specify a R version the latest
+released version will be used (currently R 3.6). You can also specify the exact
+patch release you want to use for the 3.5 and 3.6 series.
To see an example R repository, visit our `R
example in binder-examples <https://github.com/binder-examples/r/blob/master/runtime.txt>`_.

MODIFY
docs/source/faq.rst
docs/source/faq.rst
@@ -49,10 +49,11 @@ Julia versions 0.6.x and earlier are supported via a :ref:`REQUIRE <REQUIRE>` fi
R
~
-Only R 3.4.4 is currently supported, which is installed via ``apt`` from the
-`ubuntu bionic repository <https://packages.ubuntu.com/bionic/r-base>`_.
-
+The default version of R is currently R 3.6.1. You can select the version of
+R you want to use by specifying it in the :ref:`runtime.txt <runtime.txt>`
+file.
+We support R versions 3.4, 3.5 and 3.6.
Why is my repository is failing to build with ``ResolvePackageNotFound`` ?

Update R version documentation