## How do I open R help about a symbol, special character, or punctuation mark like ( parenthesis or [ bracket?

A question I’ve googled before without success. Hopefully this answer will show up for someone who needs it. I’ll also go over the better-known uses of `?` just in case.

• To get help in `R` about a function like `subset` you type `?subset` . That’s like `man subset` from the command line.
• If you only know roughly what you’re looking for use double question marks: so `??nonlinear` will lead to the package `nlme`. That’s like `apropos` on the command line.
• To get a package overview, type `?xts::xts`. There is no `?xts` help. Packages that don’t have `?twitteR::twitteR` you will need to use `??twitteR` to find the help pages on `?twitteR::status-class`, `?twitteR::dmGet`, etc.
• Finally, the question of the title. To get R help on punctuation such as `(`,` {`, `[`, ```, `::`,` ...`,` +`, and yes, even on `?` itself, use single quotes to ‘escape’ the meaningful symbol. Examples follow:
• `?'`'`
• `?'('`
• `?'['`
• `?'...'`
• `?'+'`
• `?'%*%'`
• `?'%x%'`
• `?'%o%'`
• `?'%%'`
• `?'%/%'`
• `?'\$'`
• `?'^'`
• `?'~'`
• `?'<-'`
• `?'='`
• `?'<<-'`

All of the quotation marks ```, `'`, `"` use the same help file so `?'"'` or `?'`'` will give you the help file for `?'''`.

$\dpi{200} \bg_white \large \begin{bmatrix}c_1+c_2 & -c_2 & 0 \\ -c2 & c_2 + c_3 & - c_3 \\ 0 & -c_3 & c_3 + c_4 \end{bmatrix}$

$\dpi{200} \bg_white \large \begin{vmatrix}c_1+c_2 & -c_2 \\ -c2 & c_2 + c_3 \end{vmatrix} = c_1 c_2 + c_2 c_3 + c_1 c_3$

FREAKY

(Source: ocw.mit.edu)

hi-res

Scepticism trades on [1] a focus on the worst case, and [2] a demand that any method of forming belief find the truth in all logically possible circumstances.

When action must be taken, scepticism is in league with obscurantism, with know-nothingism, and in opposition to forces that are more optimistic about the information that inquiry can provide to judgement.
Clark Grymour

(Source: hss.cmu.edu)

my illustration of the first isomorphism theorem, which says you can replace an arrow `ƒ:X→Y` by a sequence of arrows `surjection ∘ bijection ∘ injection`.

(Source: tjsullivan.org.uk)

Lebesgue’s approach to integration was summarized in a letter to Paul Montel. He writes:

I have to pay a certain sum, which I have collected in my pocket. I take the bills and coins out of my pocket and give them to the creditor in the order I find them until I have reached the total sum. This is the Riemann integral. But I can proceed differently. After I have taken all the money out of my pocket I order the bills and coins according to identical values and then I pay the several heaps one after the other to the creditor. This is my integral.
Siegmund-Schultze, Reinhard (2008), “Henri Lebesgue”, in Timothy Gowers, June Barrow-Green, Imre Leader, Princeton Companion to Mathematics

(Source: Wikipedia)

Cityscape 1 (Landscape #1)  by Richard Diebenkorn, 1963

hi-res

I loved being a rifle company commander. Having the responsibility for 211 men. Being totally in charge of their welfare and their training. That was the happiest period of my life, professionally, looking back on things.

Craftsman Selling Cases by a Teak-Wood Building by Edwin Lord Weeks

Oil on canvas, c.1885, 99.7 x 73 cm. Private collection.

hi-res

risk, however measured, is not positively related to (rational) expected returns. It goes up a bit as you go from Treasuries, or overnight loans, to the slightly less safe BBB bonds, or 3 year maturities. But that’s it, that’s all you get for merely taking the psychic pain of risk.

Just as septic tank cleaners do not make more than average, or teachers of unruly students do not make more than average, merely investing in something highly volatile does not generate automatic compensation. Getting rich has never been merely an ability to withstand some obvious discomfort.