R语言–plotmath

四大常用的数学软件是Matlab（数值计较）、Maple（代数）、Mathematica（代数和数值计较）和Sas(统计)，它们都不是免费的。与之对应的免费软件是Scilab（数值计较）、Maxima（代数）和R（统计）。

R的绘图有很好的数学公式成果，详细利用是操作text()语句中放入expression表达的数学公式。利用plot等等语句画出图形后，用text()在图形中插手文字，而expression中的语句将会被表明为数学公式。

譬喻：
plot(1,2) # 在(1,2)处画一个点
text(1,1.9,expression_r(hat(x))) # 在(1,1.9)处插手\hat{x}

expression_r()中可以利用的数学表达式如下，比Latex少，可是比matlab多。

【注：下面摘自R语言的参考文件plotmath一节】
x + y x plus y
x – y x minus y
x*y juxtapose x and y
x/y x forwardslash y
x %+-% y x plus or minus y
x %/% y x divided by y
x %*% y x times y
x %.% y x cdot y
x[i] x subscript i
x^2 x superscript 2
paste(x, y, z) juxtapose x, y, and z
sqrt(x) square root of x
sqrt(x, y) yth root of x
x == y x equals y
x != y x is not equal to y
x < y x is less than y
x <= y x is less than or equal to y
x > y x is greater than y
x >= y x is greater than or equal to y
x %~~% y x is approximately equal to y
x %=~% y x and y are congruent
x %==% y x is defined as y
x %prop% y x is proportional to y
plain(x) draw x in normal font
bold(x) draw x in bold font
italic(x) draw x in italic font
bolditalic(x) draw x in bolditalic font
symbol(x) draw x in symbol font
list(x, y, z) comma-separated list
… ellipsis (height varies)
cdots ellipsis (vertically centred)
plotmath 663
ldots ellipsis (at baseline)
x %subset% y x is a proper subset of y
x %subseteq% y x is a subset of y
x %notsubset% y x is not a subset of y
x %supset% y x is a proper superset of y
x %supseteq% y x is a superset of y
x %in% y x is an element of y
x %notin% y x is not an element of y
hat(x) x with a circumflex
tilde(x) x with a tilde
dot(x) x with a dot
ring(x) x with a ring
bar(xy) xy with bar
widehat(xy) xy with a wide circumflex
widetilde(xy) xy with a wide tilde
x %<->% y x double-arrow y
x %->% y x right-arrow y
x %<-% y x left-arrow y
x %up% y x up-arrow y
x %down% y x down-arrow y
x %<=>% y x is equivalent to y
x %=>% y x implies y
x %<=% y y implies x
x %dlup% y x double-up-arrow y
x %dldown% y x double-down-arrow y
alpha – omega Greek symbols
Alpha – Omega uppercase Greek symbols
theta1, phi1, sigma1, omega1 cursive Greek symbols
Upsilon1 capital upsilon with hook
aleph first letter of Hebrew alphabet
infinity infinity symbol
partialdiff partial differential symbol
nabla nabla, gradient symbol
32*degree 32 degrees
60*minute 60 minutes of angle
30*second 30 seconds of angle
displaystyle(x) draw x in normal size (extra spacing)
textstyle(x) draw x in normal size
scriptstyle(x) draw x in small size
scriptscriptstyle(x) draw x in very small size
underline(x) draw x underlined
x ~~ y put extra space between x and y
x + phantom(0) + y leave gap for “0”, but don’t draw it
x + over(1, phantom(0)) leave vertical gap for “0” (don’t draw)
frac(x, y) x over y
over(x, y) x over y
atop(x, y) x over y (no horizontal bar)
sum(x[i], i==1, n) sum x[i] for i equals 1 to n
prod(plain(P)(X==x), x) product of P(X=x) for all values of x
integral(f(x)*dx, a, b) definite integral of f(x) wrt x
union(A[i], i==1, n) union of A[i] for i equals 1 to n
intersect(A[i], i==1, n) intersection of A[i]
664 plotmath
lim(f(x), x %->% 0) limit of f(x) as x tends to 0
min(g(x), x > 0) minimum of g(x) for x greater than 0
inf(S) infimum of S
sup(S) supremum of S
x^y + z normal operator precedence
x^(y + z) visible grouping of operands
x^{y + z} invisible grouping of operands
group(“(“,list(a, b),”]”) specify left and right delimiters
bgroup(“(“,atop(x,y),”)”) use Scalable delimiters
group(lceil, x, rceil) special delimiters