some doc install changes for 0.9.73

doc/installation.rst

@@ -215,24 +215,24 @@ installation.
 .. _install-conda:
 
 Installing into an existing Anaconda Python environment
-================================================================
+=========================================================
 
-If you are already using an `Anaconda Python`_  environment, you may want to
-install Larch into that environment or create a new environment for it.
-Larch uses many of the common "scipy ecosystem" packages. The main packages
-that you may need to install that may not be installed are:
+If are already using an existing `Anaconda Python`_, you may want to install
+Larch into that environment or create a new environment for it.  This is
+definitely possible.  Larch uses many of the common "scipy ecosystem"
+packages. The main packages that you may need to install that may not be
+installed are:
 
    * `wxpython`: needed for all plotting, graphics and GUI applications.
    * `pymatgen`: needed for handling CIF files to generate Feff input files.
    * `openbabel`: needed for converting some structure files to Feff input files.
    * `tomopy`: needed only for reconstructing X-ray fluorescence tomography.
-   * `epicsapps`: applications using the Epics control system.
 
 To be clear, much of the core Larch functionality can be used as a library
 without these packages installed, but especially `wxpython` and `pymatgen` are
 heavily used and should be installed.
 
-There is a `conda-forge` package for X-ray Larch, so from a shell it may be
+If you are using There is a `conda-forge` package for X-ray Larch, so from a shell it may be
 that all you need to do is run
 
 
@@ -267,12 +267,84 @@ Finally, no matter how you install Larch, you can run
 
 to create the Larch desktop application launchers or shortcuts.
 
+Installing with `pip` into an existing Python environment
+===========================================================
+
+Larch relies on the "scipy ecosystem", and has a large number of packages that
+it depends on. Most of these are available as binary (so-called "wheel" files)
+from `PyPI`_, so that a simple
+
+.. code:: bash
+
+    pip install xraylarch
+
+will work. In fact, as of this writing (0.9.73, November, 2023), this install
+command will work to install a fairly bare-bones set of tools -- the basic
+xraylarcg library, without requiring the packages needed to make any of the
+GUIs work.
+
+In order to get the GUI-needed package, you could install with
+
+.. code:: bash
+
+    pip install xraylarch[larix]
+
+(Note, you may need to type "``pip install xraylarch\[larix\]``" in some shells
+and terminals).  This will also install all of the `wxPython` packages needed
+for the GUIs, as well as the libraries related to Jupyter.
+
+The most notable missing binary package is the `wxPython` package on Linux.
+That means that if `wxPython` is not already installed, `pip` will try to
+compile it: this will almost certainly fail.  This problem (which, in fairness
+to all involved, is very difficult to solve) is one of the main reasons we
+recommend using `Anaconda Python` - it provides this package in a consistent
+way. Anaconda Python also provides very good versions of almost all of hte
+"core scipy ecosystem" libraries.  It also has good support for optional Intel
+Math Kernel libraries that will be used if available.
+
+But, if you are not using Linux, or are using a system-provided Python that
+includes wxPython (and has it installed), it should be possible to install a
+runnable Larch library with
+
+.. code:: bash
+
+    pip install xraylarch
+
+There are other optional addons that can be installed with Larch, such as
+
+.. code:: bash
+
+    pip install xraylarch[dev]
+
+to add development and testing packages, or
+
+.. code:: bash
+
+    pip install xraylarch[doc]
+
+to add tools needed to build the docs, or
+
+.. code:: bash
+
+    pip install xraylarch[epics]
+
+to add tools needed to use the Epics controls system, or
+
+.. code:: bash
+
+    pip install xraylarch[all]
+
+to install all these (and a few more packages)
+
 
 Updating a previous installation
 ==================================
 
 As new versions of X-ray Larch are released, they will be announced and pushed
-to `PyPI`_, so that updating can be done with:
+
+to `PyPI`_.  This will allow updating can be done with
+
+.. code:: bash
 
     pip install --upgrade xraylarch
 
@@ -310,16 +382,22 @@ Making Desktop shortcuts to Link to the Applications
 =======================================================
 
 To make a `Larch` folder on your desktop with shortcuts (Windows or Linux) or
-Applications (MacOS) for the main Larch applications, you can then type::
+Applications (MacOS) for the main Larch applications, you can then type
+
+.. code:: bash
 
     larch -m
 
 If that complains that it does not find `larch`, you may have to explicitly
-give the path to Python and/or Larch::
+give the path to Python and/or Larch
+
+.. code:: bash
 
    $HOME/xraylarch/bin/larch -m
 
-from Linux or MacOSX or::
+from Linux or MacOSX or
+
+.. code:: bash
 
    %APPDATA%\\Local\\xraylarch\Scripts\larch.exe -m
 
@@ -343,16 +421,16 @@ the source repository with::
 
 and then install with::
 
-    pip install -e .
+    pip install -e .[all]
 
 This use of `pip` will install any requirements and Larch itself, but those
 should have been installed already when you installed.  Depending on your
 platform and version of Python you are installing to, you may need elevated
 permissions as from `sudo` to install Larch to a system folder.
 
 
-Optional Python Packages
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Installing Optional Python Packages with Larch
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 While most of the packages required for Larch will be installed automatically
 (and are listed in the `requirements.txt` file in the source tree), there are