I just realized that there were loads of really useful mathematic symbols when you hold down the Option key on my MacBook.
≤ ≥ ≠ ÷ • « ∑ √
It’s like a wonderland of mathematical symbols and I would love to map these to different functions in R, for wonderous coding.
Edit - I should clarify, I don’t want to set them as variable names, I was hoping to use them in functions. For example ∑ is the mathematical symbol for sum, so:
∑() <- base::sum()
Or square root
√() <- base::sqrt()
Only problem, of course, is that R doesn’t recognize them.
Unexpected Input
I generally program in the Terminal too. Is there any way to force R to recognize special characters?
Related
I'd like something to convert pretty basic math expressions, having nested parentheses and fractions, to LaTeX notation. Like mathquill, but a function (or even the building blocks of one).
There seem to be some Lua and Haskell solutions in a pandoc/Rmarkdown context, but I can't use those, because (a) I'm scared of real languages, and (b) I'm generating PNGs (via webtex) to be featured in a flextable table, outside of a rendered document.
I'm inexperienced with regular expressions, so I don't know how to leverage something like this, but I'd appreciate any pointers if that seems like a productive path.
"Write a parser" is something best left to others, at least in my case!
Example expression below. Just a few levels of nesting, no big deal. I can bound it at, say, 5 levels, if that helps. And the input is parseable as an R expression—I can guarantee matched parentheses, for example.
(y0 - (y0/((1-y0)*exp(B*dx)+y0)))*Pop
Here's what I'd want in the case above. The \cdots are sugar; I can handle those.
\left(y0-\frac{y0}{\left(1-y0\right)\cdot\exp\left(B\cdot dx\right)+y0}\right)\cdot Pop
Visually:
i made a rsa-encryption demo to learn julia but ran into a problem.
this should be no issue of overflow and all values fit rsa criteria when i check with python code.
any pointers are welcome. julia is an awesome language and i would like to figure this out.
check these images to see my problem:
You need BigInt(message)^used_e, and similar. The problem you are seeing is integer overvflow before you convert to BigInt. Note that powermod(BigInt(message), used_e, used_N) will be much faster since it will keep all the intermediate numbers smaller.
Note that in Julia x % y is a synonym for the rem(x, y) function “from Euclidean division, returning a value of the same sign as x”, whereas for an RSA implementation, you need the mod function instead, where the result has the same sign as y. (But you really actually want powermod over BigInt here for performance.)
I am attempting to create a linear combination of two numbers to create their GCD. The code I have so far can find the expanded solution. I have done all of the (hard) math for it (i.e. find the GCD using Euclid's Algorithm, then work backward essentially) and it will result in something like this for example (the two starting numbers are 1215 and 960):
((960-(3*(1215-(1*960))))-(3*((1215-(1*960))-(1*(960-(3*(1215-(1*960))))))))
In my actual solution there is a space between every component (e.g. '( ( 960 - (3 * '...)
but I am trying to simplify this into the equation:
((-15*1215)+(19*960))
I feel like the best approach is to create an Expression Tree, but I don't know how to without actually just evaluating the answer.
It sounds like you are looking for a symbolic computation system. Here's one approach using Maxima (https://maxima.sourceforge.net). I'll enable stardisp to show * between terms of a product. I'll also input numbers like 960 as symbols in order to suppress arithmetic on them by writing them as \960 etc. Note that 1 and 3 are input as ordinary numbers so arithmetic is carried out on them.
(%i13) stardisp:true;
(%o13) true
(%i14) 2*3;
(%o14) 6
(%i15) \2*\3;
(%o15) 2*3
(%i16) ((\960-(3*(\1215-(1*\960))))-(3*((\1215-(1*\960))-(1*(\960-(3*(\1215-(1*\960))))))));
(%o16) 960 - 3*(1215 - 960) - 3*((- 2*960) + 3*(1215 - 960)
+ 1215)
(%i17) factor(%);
(%o17) 19*960 - 15*1215
Maybe you want to replace the numbers with symbols a, b, c, etc to get a more general solution.
There are many other symbol computation systems, a web search will find them. Good luck and have fun.
I am writing the documentation for a function of an R package I am building.
In order to have a moderately nice aspect for the help file, I need the equivalent of \bar{x} in ASCII:
\eqn{\bar{x}}{ASCII equivalent}
Not sure there's a consensus on the best way to do this, it's more a matter of taste and clarity.
Having faced this issue myself, two solutions I have used are:
y = \eqn{\bar{x}}{xbar}
y = \eqn{\bar{x}}{mean(x)}
The advantage of the latter is that when the help is displayed as ASCII, the user can copy/paste (send) the text to an R process, getting an example value for y. This assumes that \bar{x} is shorthand for the mean, as is often the case.
I like solving my math problems(high school) using R as it is faster than writing on a piece of paper. One problem I'm having is that I have to keep writing the multiplication sign, example:
9x^2 + 24x + 16 yields = Error: unexpected symbol in "9x"
Is there any way in R to multiply 4x, without having to write 4*x but only 4x?
Would save me some time in having to write one extra character the whole time! Thanks
No. Having a number in front of a character without any space simply isn't valid syntax in R.
Take a step back and look at the syntax rules for, say, Excel, Matlab, Python, Mathematica. Every language has its rules, generally (:-) ) with good reason. For example, in R, the following are legal object names:
foo
foo.bar
foo1
foo39
But 39foo is not legal. So if you wanted any sequence [0-9][Letters] or the reverse to indicate multiplication, you'd have a conflict with naming rules.