## 3.4. Functions

This section contains information on all functions in the Cypher query language.

Note that related information exists in Section 3.2.5, “Operators”.

Most functions in Cypher will return `null` if an input parameter is `null`.

Predicate functions

These functions return either true or false for the given arguments.

Function Description

all()

Tests whether the predicate holds for all elements in a list.

any()

Tests whether the predicate holds for at least one element in a list.

exists()

Returns true if a match for the pattern exists in the graph, or if the specified property exists in the node, relationship or map.

none()

Returns true if the predicate holds for no element in a list.

single()

Returns true if the predicate holds for exactly one of the elements in a list.

Scalar functions

These functions return a single value.

Function Description

coalesce()

Returns the first non-`null` value in a list of expressions.

endNode()

Returns the end node of a relationship.

Returns the first element in a list.

id()

Returns the id of a relationship or node.

last()

Returns the last element in a list.

length()

Returns the length of a path.

properties()

Returns a map containing all the properties of a node or relationship.

size()

Returns the number of items in a list.

size() applied to pattern expression

Returns the number of sub-graphs matching the pattern expression.

size() applied to string

Returns the size of a string.

startNode()

Returns the start node of a relationship.

timestamp()

Returns the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC.

toBoolean()

Converts a string value to a boolean value.

toFloat()

Converts an integer or string value to a floating point number.

toInteger()

Converts a floating point or string value to an integer value.

type()

Returns the string representation of the relationship type.

Aggregating functions

These functions take multiple values as arguments, and calculate and return an aggregated value from them.

Function Description

avg()

Returns the average of a set of numeric values.

collect()

Returns a list containing the values returned by an expression.

count()

Returns the number of values or rows.

max()

Returns the maximum value in a set of values.

min()

Returns the minimum value in a set of values.

percentileCont()

Returns the percentile of a value over a group using linear interpolation.

percentileDisc()

Returns the nearest value to the given percentile over a group using a rounding method.

stDev()

Returns the standard deviation for the given value over a group for a sample of a population.

stDevP()

Returns the standard deviation for the given value over a group for an entire population.

sum()

Returns the sum of a set of numeric values.

List functions

These functions return lists of other values. Further details and examples of lists may be found in Section 3.2.8, “Lists”.

Function Description

extract()

Returns a list `lresult` containing the values resulting from an expression which has been applied to each element in a list `list`.

filter()

Returns a list `lresult` containing all the elements from a list `list` that comply with a predicate.

keys()

Returns a list containing the string representations for all the property names of a node, relationship, or map.

labels()

Returns a list containing the string representations for all the labels of a node.

nodes()

Returns a list containing all the nodes in a path.

range()

Returns a list comprising all integer values within a specified range.

reduce()

Runs an expression against individual elements of a list, storing the result of the expression in an accumulator.

relationships()

Returns a list containing all the relationships in a path.

reverse()

Returns a list in which the order of all elements in the original list have been reversed.

tail()

Returns all but the first element in a list.

Mathematical functions - numeric

These functions all operate on numerical expressions only, and will return an error if used on any other values.

Function Description

abs()

Returns the absolute value of a number.

ceil()

Returns the smallest floating point number that is greater than or equal to a number and equal to a mathematical integer.

floor()

Returns the largest floating point number that is less than or equal to a number and equal to a mathematical integer.

rand()

Returns a random floating point number in the range from 0 (inclusive) to 1 (exclusive); i.e. `[0,1)`.

round()

Returns the value of a number rounded to the nearest integer.

sign()

Returns the signum of a number: `0` if the number is `0`, `-1` for any negative number, and `1` for any positive number.

Mathematical functions - logarithmic

These functions all operate on numerical expressions only, and will return an error if used on any other values.

Function Description

e()

Returns the base of the natural logarithm, `e`.

exp()

Returns `e^n`, where `e` is the base of the natural logarithm, and `n` is the value of the argument expression.

log()

Returns the natural logarithm of a number.

log10()

Returns the common logarithm (base 10) of a number.

sqrt()

Returns the square root of a number.

Mathematical functions - trigonometric

These functions all operate on numerical expressions only, and will return an error if used on any other values.

All trigonometric functions operate on radians, unless otherwise specified.

Function Description

acos()

Returns the arccosine of a number in radians.

asin()

Returns the arcsine of a number in radians.

atan()

Returns the arctangent of a number in radians.

atan2()

Returns the arctangent2 of a set of coordinates in radians.

cos()

Returns the cosine of a number.

cot()

Returns the cotangent of a number.

degrees()

haversin()

Returns half the versine of a number.

pi()

Returns the mathematical constant pi.

sin()

Returns the sine of a number.

tan()

Returns the tangent of a number.

String functions

These functions are used to manipulate strings or to create a string representation of another value.

Function Description

left()

Returns a string containing the specified number of leftmost characters of the original string.

lTrim()

Returns the original string with leading whitespace removed.

replace()

Returns a string in which all occurrences of a specified string in the original string have been replaced by another (specified) string.

reverse()

Returns a string in which the order of all characters in the original string have been reversed.

right()

Returns a string containing the specified number of rightmost characters of the original string.

rTrim()

Returns the original string with trailing whitespace removed.

split()

Returns a list of strings resulting from the splitting of the original string around matches of the given delimiter.

substring()

Returns a substring of the original string, beginning with a 0-based index start and length.

toLower()

Returns the original string in lowercase.

toString()

Converts an integer, float or boolean value to a string.

toUpper()

Returns the original string in uppercase.

trim()

Returns the original string with leading and trailing whitespace removed.

Spatial functions

These functions are used to specify points in a 2D coordinate system and to calculate the geodesic distance between two points.

Function Description

distance()

Returns a floating point number representing the geodesic distance between any two points in the same CRS.

point() - cartesian 2D

Returns a point object, given two coordinate values in the cartesian coordinate system.

point() - WGS 84

Returns a point object, given two coordinate values in the WGS 84 coordinate system.