表达式

表达式说明

目前表达式支持的功能

目前仅支持$feature链接符，支持访问要素的属性信息。 example

$feature.FID //表示访问要素的FID字段

支持一般通用数学运算符，如+-*/等计算符

example

计算面积占比

$feature.AREA/$feature.TOTALAREA

example

支持 || and or >= <=等

$feature.ISAREA || $feature.ISRIVER

Operator	Associativity	Description
(...)	None	Grouping
f(), x.y, a[i]	Left	Function call, property access, array indexing
!	Left	Factorial
^	Right	Exponentiation
+, -, not, sqrt, etc.	Right	Unary prefix operators (see below for the full list)
*, /, %	Left	Multiplication, division, remainder
+, -, \|\|	Left	Addition, subtraction, array/list concatenation
==, !=, >=, <=, >, <, in	Left	Equals, not equals, etc. "in" means "is the left operand included in the right array operand?"
and	Left	Logical AND
or	Left	Logical OR
x ? y : z	Right	Ternary conditional (if x then y else z)
=	Right	Variable assignment
;	Left	Expression separator

Operator	Description
-x	Negation
+x	Unary plus. This converts it's operand to a number, but has no other effect.
x!	Factorial (x * (x-1) * (x-2) * … * 2 * 1). gamma(x + 1) for non-integers.
abs x	Absolute value (magnitude) of x
acos x	Arc cosine of x (in radians)
acosh x	Hyperbolic arc cosine of x (in radians)
asin x	Arc sine of x (in radians)
asinh x	Hyperbolic arc sine of x (in radians)
atan x	Arc tangent of x (in radians)
atanh x	Hyperbolic arc tangent of x (in radians)
cbrt x	Cube root of x
ceil x	Ceiling of x — the smallest integer that’s >= x
cos x	Cosine of x (x is in radians)
cosh x	Hyperbolic cosine of x (x is in radians)
exp x	e^x (exponential/antilogarithm function with base e)
expm1 x	e^x - 1
floor x	Floor of x — the largest integer that’s <= x
length x	String length of x
ln x	Natural logarithm of x
log x	Natural logarithm of x (synonym for ln, not base-10)
log10 x	Base-10 logarithm of x
log2 x	Base-2 logarithm of x
log1p x	Natural logarithm of (1 + x)
not x	Logical NOT operator
round x	X, rounded to the nearest integer, using "grade-school rounding"
sign x	Sign of x (-1, 0, or 1 for negative, zero, or positive respectively)
sin x	Sine of x (x is in radians)
sinh x	Hyperbolic sine of x (x is in radians)
sqrt x	Square root of x. Result is NaN (Not a Number) if x is negative.
tan x	Tangent of x (x is in radians)
tanh x	Hyperbolic tangent of x (x is in radians)
trunc x	Integral part of a X, looks like floor(x) unless for negative number

Function	Description
random(n)	Get a random number in the range [0, n). If n is zero, or not provided, it defaults to 1.
fac(n)	n! (factorial of n: "n * (n-1) * (n-2) * … * 2 * 1") Deprecated. Use the ! operator instead.
min(a,b,…)	Get the smallest (minimum) number in the list.
max(a,b,…)	Get the largest (maximum) number in the list.
hypot(a,b)	Hypotenuse, i.e. the square root of the sum of squares of its arguments.
pyt(a, b)	Alias for hypot.
pow(x, y)	Equivalent to x^y. For consistency with JavaScript's Math object.
atan2(y, x)	Arc tangent of x/y. i.e. the angle between (0, 0) and (x, y) in radians.
roundTo(x, n)	Rounds x to n places after the decimal point.
map(f, a)	Array map: Pass each element of `a` the function `f`, and return an array of the results.
fold(f, y, a)	Array fold: Fold/reduce array `a` into a single value, `y` by setting `y = f(y, x, index)` for each element `x` of the array.
filter(f, a)	Array filter: Return an array containing only the values from `a` where `f(x, index)` is `true`.
indexOf(x, a)	Return the first index of string or array `a` matching the value `x`, or `-1` if not found.
join(sep, a)	Concatenate the elements of `a`, separated by `sep`.
if(c, a, b)	Function form of c ? a : b. Note: This always evaluates both `a` and `b`, regardless of whether `c` is `true` or not. Use `c ? a : b` instead if there are side effects, or if evaluating the branches could be expensive.
when(case,value,case,value,defaultValue)	条件语句