Apply suggestions from code review

Co-authored-by: Ryan Curtin <ryan@ratml.org>
Co-authored-by: James J Balamuta <coatless@users.noreply.github.com>

README.md

@@ -122,7 +122,7 @@ If you would like to build the Julia bindings, make sure that Julia >= 1.3.0 is
 installed.
 
 If you would like to build the Go bindings, make sure that Go >= 1.11.0 is
-installed with this package.
+installed with this package:
 
      gonum
 

doc/guide/r_quickstart.hpp

@@ -13,15 +13,17 @@ This quickstart guide is also available for @ref python_quickstart "Python"
 @ref cli_quickstart "the command-line", @ref julia_quickstart "Julia" and
 @ref go_quickstart "Go".
 
-@section r_quickstart_install Installing mlpack
+@section r_quickstart_install Installing mlpack binary package
 
 Installing the mlpack bindings for R is straightforward; you can just use
-cran mirror:
+CRAN mirror:
 
 @code{.R}
 install.packages('mlpack')
 @endcode
 
+@section r_quickstart_install Installing mlpack package from source
+
 Building the R bindings from scratch is a little more in-depth, though.  For
 information on that, follow the instructions on the @ref build page, and be sure
 to specify @c -DBUILD_R_BINDINGS=ON to CMake; you may need to also set the
@@ -167,9 +169,7 @@ Recommendations for user 1:
 
 @section r_quickstart_nextsteps Next steps with mlpack
 
-Now that you have done some simple work with mlpack, you have seen how it can
-easily plug into a data science workflow in R.  A great thing to do next
-would be to look at more documentation for the R mlpack bindings:
+After working through this overview to `mlpack`'s R package, we hope you are inspired to use `mlpack`' in your data science workflow.  We recommend as part of your next steps to look at more documentation for the R mlpack bindings:
 
  - <a href="https://www.mlpack.org/doc/mlpack-git/r_documentation.html">R mlpack
    binding documentation</a>

src/mlpack/bindings/R/print_type_doc_impl.hpp

@@ -53,7 +53,7 @@ std::string PrintTypeDoc(
   // Not sure what it is...
   else
   {
-    throw std::invalid_argument("unknown parameter type " + data.cppType);
+    throw std::invalid_argument("Unknown parameter type '" + data.cppType + "'.");
   }
 }
 
@@ -75,7 +75,7 @@ std::string PrintTypeDoc(
   }
   else
   {
-    throw std::invalid_argument("unknown vector type " + data.cppType);
+    throw std::invalid_argument("Unknown vector type '" + data.cppType + "'.");
   }
 }
 
@@ -117,7 +117,7 @@ std::string PrintTypeDoc(
   }
   else
   {
-    throw std::invalid_argument("unknown matrix type " + data.cppType);
+    throw std::invalid_argument("Unknown matrix type '" + data.cppType + "'.");
   }
 }