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Frequently Asked Questions

WReach? Is that connected to WRI somehow?

The "WR" in my name has nothing to do with the company that develops Mathematica. It is just a coincidence.

Why do you start all your global variable names with $?

I use dollar signs for ad hoc global variables because I have been bitten too many times by accidentally assigning an own-value to a symbol that I happen to use, for example, in a symbolic equation. So I am in the habit of writing $x instead of x. I stick to that convention even for longer symbols like $initialUrl. Just like the regular symbol convention, Mathematica's predefined global symbols all start with a capital letter after the $. My ad hoc symbols always start with a lower case letter, so there is no conflict.

Why do you put semicolons and commas at the beginning of the line instead of at the end like a normal person?

I don't think of it that way. Rather, I switch from horizontal to vertical layout when a single expression is too long to fit on one line. This has the interesting side-effect of making the important delimiters stand out and line up. I first ran into this practice in the SQL community. SQL "programs" have the unpleasant property that they must be written as a single statement -- even if that statement is a hundred lines long (or more!). Sometimes Mathematica expressions share that property.


Jul
26
comment AssociationMap to query Dataset across levels?
Okay, I think I finally see what you are after -- fingers crossed :). Please see my all-new response.
Jul
26
revised AssociationMap to query Dataset across levels?
all-new response using `Query`
Jul
26
awarded  Enlightened
Jul
26
awarded  Nice Answer
Jul
26
revised Geographic background containing both outlines and contours: how?
the options were reversed from their titles
Jul
26
revised Geographic background containing both outlines and contours: how?
added the screenshot that shows the mismatch between the point and polygon coordinates
Jul
26
answered Geographic background containing both outlines and contours: how?
Jul
25
revised AssociationMap to query Dataset across levels?
added the inline version of `baz`
Jul
25
revised AssociationMap to query Dataset across levels?
minor code cliean-up for `baz`
Jul
25
revised AssociationMap to query Dataset across levels?
fixed a typo
Jul
25
comment AssociationMap to query Dataset across levels?
Please see the new section in my response, "starting from titanicClass".
Jul
25
revised AssociationMap to query Dataset across levels?
added the section "starting from titanicClass"
Jul
25
answered AssociationMap to query Dataset across levels?
Jul
24
comment Mathematica 10 : Where is the Mathematica Book?
This is a duplicate of Where (have) the “Function Navigator” and “Virtual Book” gone?.
Jul
23
answered Populate an upper triangular matrix from a vector of elements
Jul
22
answered Get the last line from each of a large number of files, transform them, and write all results to a single new file
Jul
21
comment Report: IgnoringInactive: a bug?
On a related note, MatchQ[1, IgnoringInactive[0]] and MatchQ["a", IgnoringInactive["b"]] both return True instead of False (reported to WRI).
Jul
21
awarded  Informed
Jul
19
answered Caesar's cipher
Jul
18
awarded  Nice Answer