# References

There are several ways to figure out how to do something in ROOT:

-   The ROOT web site. As of 2023, these are the areas of the [ROOT
    manual](https://root.cern/manual/) on that site which are supposed
    to act as documentation:

    -   The [ROOT Reference](https://root.cern/doc/master/index.html).
        You've already visited this area. It contains the detailed
        description of the ROOT classes.

    -   [ROOT Basics](https://root.cern/manual/basics/). The web pages
        here outline a basic approach to ROOT. They assume you're already
        familiar with C++ or Python. It's especially useful if you don't
	need the step-by-step hand-holding approach I took in this tutorial.

    -   [ROOT Functional
        Parts](https://root.cern/manual/functional_parts/). While this
        describes the ROOT classes, it does so from a technical
        perspective rather than act as a teaching guide. For example,
        take a look at their [introduction to
        histograms](https://root.cern/manual/histograms/) to see if its
        approach works for you.

<p />

-   The [ROOT User's
    Guide](https://root.cern/root/htmldoc/guides/users-guide/ROOTUsersGuide.html).
    As I've mentioned before, this is a bit out-of-date; it has not been
    revised since 2018 (and it appears it [never will
    be](https://root.cern/blog/manual-week/)). For example, there's
    nothing in that guide about {ref}`RDataFrames <rdataframe>`. 
    But I feel it's a much better tutorial for new users
    than any of the other items on this list.[^f98]

<p />

-   Create something "by hand," save it as a .C file, then examine the
    file to see how ROOT does it.

There's one other resource: the example ROOT programs that come with the
package. There's a ROOT-based command that will tell you where they are:

    root-config --tutdir

When I ask myself the question "How do I do something complicated in
ROOT?" I often find the answer in one of the examples they provide.

I've found it handy to make my own copy:[^f99]

    > cp -arv `root-config --tutdir` $PWD

Then I go into the "tutorials" sub-directory, run their examples, and
look at their code:

    > cd tutorials
    > root demos.C
    > cd graphics
    > root first.C
    > less first.C

You can also find the
[tutorials](https://root.cern/doc/master/group__Tutorials.html) on the
ROOT web site, but I find it harder to search for specific examples.

:::{admonition} The documentation is all over the place!
:class: note

If the distributed nature of the information is annoying to you, welcome
to the club! I often have to go hunting to find the answers I want when
using ROOT, even after years of working with the package.

Occasionally I've had no other choice but to examine the C++ source
code of the ROOT program itself to find out the answer to a question.

:::

:::{figure-md} teaching_physics-fig
:class: align-center

<img src="https://imgs.xkcd.com/comics/teaching_physics.png" alt="xkcd teaching_physics" width="75%">

<https://xkcd.com/895/> by Randall Munroe. 
Perhaps this is the reason why the ROOT web site no longer teaches its
concepts from scratch. It definitely explains the cartoons and jokes in
this tutorial.
:::

[^f98]: So what ROOT resources are out there that are both up-to-date and
    suitable for students who are not familiar with programming or
    data-analysis concepts? Unfortunately, the only one I know of is the
    tutorial you're reading now!

[^f99]: I'm being tricky here by using the
    [backtick](https://unix.stackexchange.com/questions/27428/what-does-backquote-backtick-mean-in-commands)
    in a UNIX command. In this particular case, what this does is take the
    output of the command `root-config --tutdir` and insert it into the
    command.