Mathematics Operators

2023년 3월 21일 오후 1:30

Introduced in v5.1.20The mathematics filter operators allow numerical calculations to be performed within filters.

Using mathematics operators

The mathematics operators interpret their arguments as numbers according to the following rules:

Any non-numeric characters after a valid number are ignored (e.g. 28px is interpreted as the number 28)
If the argument cannot be interpreted as a number, the value 0 is used (e.g. foo is interpreted as the number 0)
The special values Infinity and -Infinity can be used to represent positive and negative infinity respectively

Warning

Some filter operators remove duplicate items which can cause unexpected results when using the mathematics operators. See Dominant Append for details.

The mathematics operators take three different forms:

Unary operators apply an operation to each number in the input list (e.g. negate, truncate, sign)
- =1 =2 =3 =4 +[negate[]]evaluates to-1-2-3-4
- =1.2 =2.4 =3.6 =4.8 +[trunc[]]evaluates to1234
- =1.2 =2.4 =3.6 =4.8 +[round[]]evaluates to1245
Binary operators apply an operation and parameter to each number in the input list (e.g. add, multiply, remainder)
- =1 =2 =3 =4 +[add[3]]evaluates to4567
- =1 =2 =3 =4 +[multiply[8]]evaluates to8162432
Reducing operators apply an operation to all of the numbers in the input list, returning a single result (e.g. sum, product)
- =1 =2 =3 =4 +[sum[]]evaluates to10
- =1 =2 =3 =4 +[product[]]evaluates to24
- =1 =2 =3 =4 +[average[]]evaluates to2.5

Operations Combination

Operations can be combined by concatenating them while merging the inner ][ characters.

[[355]divide[113]fixed[5]]evaluates to3.14159
[range[100]sum[]divide[100]]evaluates to50.5
[tag[HelloThere]get[text]length[]sum[]]evaluates to9896

Complex operations will sometimes need to be split up into separate filters. For example, to compute the average length of the text field of tiddlers tagged "HelloThere":

<$set name="number-of-tiddlers" value={{{ [tag[HelloThere]count[]] }}}>
Average length of <$text text=<<number-of-tiddlers>>/> tiddlers tagged <<tag "HelloThere">>: <$text text={{{ [tag[HelloThere]get[text]length[]sum[]divide<number-of-tiddlers>fixed[3]] }}}/>
</$set>

That renders as:

Average length of 7 tiddlers tagged : 1413.714

Mathematics Operators list

Operator	Purpose
abs	calculate the absolute value of a list of numbers
acos	calculate the arccosine value (in radians) of a list of numbers
add	treating each input title as a number, add to each the numeric value of the parameter
asin	calculate the arcsine value (in radians) of a list of numbers
atan	calculate the arctangent value (in radians) of a list of numbers
atan2	returns the angle in the plane (in radians) between the positive x-axis and the ray from (0,0) to the point (x,y), for [`Y`]atan2[`X`]
average	treating each input title as a number, compute their arithmetic mean
ceil	rounds a list of numbers up to the next largest integer
compare	filter the input by comparing each item against the parameter
cos	calculate the cosine value of a list of angles (given in radians)
divide	treating each input title as a number, divide it by the numeric value of the parameter
exponential	convert each number to exponential notation with `N` digits
fixed	convert each number to fixed point notation with `N` digits after the decimal point
floor	rounds a list of numbers to the largest integer less than or equal to each number
log	treating each input title as a number, return its logarithm with base equal to the numeric value of the parameter if specified, otherwise base `e`
max	treating each input title as a number, take the maximum of its value and the numeric value of the parameter
maxall	find the largest of a list of numbers
median	treating each input title as a number, compute their median value
min	treating each input title as a number, take the minimum of its value and the numeric value of the parameter
minall	find the smallest of a list of numbers
multiply	treating each input title as a number, multiply it by the numeric value of the parameter
negate	calculate the negation of a list of numbers
power	treating each input title as a number, raise it to the power of the numeric value of the parameter
precision	convert each number to a string with `N` significant digits
product	produce the product of the input numbers
remainder	treating each input title as a number, return the remainder when divided by the numeric value of the parameter
round	rounds a list of numbers to the nearest integer
sign	return -1, 0 or 1 for a list of numbers according to whether each number is negative, zero, or positive
sin	calculate the sine value of a list of angles (given in radians)
standard-deviation	treating each input title as a number, compute their standard-deviation
subtract	treating each input title as a number, subtract from each the numeric value of the parameter
sum	produce the sum of the input numbers
tan	calculate the tangent value of a list of angles (given in radians)
trunc	truncates a list of numbers to their integer part, removing any fractional part
untrunc	rounds a list of numbers to the next integer with largest absolute value, that is, away from zero
variance	treating each input title as a number, compute their variance