ndarray-ops
A collection of common mathematical operations for ndarrays. Implemented using cwise
Usage
First, install the library using npm:
npm install ndarray-ops
Then you can import the library by doing:
var ops = require("ndarray-ops")
Then you can use the functions as in the following example:
//First, import librariesvar ndarray = ops = //Next, create some arraysvar a = b = c = //Initialize b with some random numbers:ops //Set c to a constant 1ops //Add b and c, store result in a:ops //Multiply a by 0.5 in placeops //Print some statistics about a:console
Conventions
This library implements component-wise operations for all of the operators and Math.* functions in JS, along with a few commonly used aggregate operations. Most of the functions in the library work by applying some symmetric binary operator to a pair of arrays. You call them like this:
ops
Which translates into code that works (approximately) like this:
forvar i=0; i<destshape0; ++i desti = arg1i + arg2i
It is up to you to specify where the result gets store. This library does not create new arrays for you to avoid performing expensive intermediate allocations. There are also a few other variations:
ops
Operators with the -eq suffix perform an assignment.
forvar i=0; i<destshape0; ++i desti += arg1i
ops
The -s suffix denotes scalar/broadcast operations; so the above would translate to:
forvar i=0; i<destshape0; ++i desti = arg1i + 10
ops
The -seq suffix is basically the combination of the above, and translates to:
forvar i=0; i<destshape0; ++i desti += 10
The following operators follow this rule:
- add[,s,eq,seq] - Addition,
+
- sub[,s,eq,seq] - Subtraction,
-
- mul[,s,eq,seq] - Multiplication,
*
- div[,s,eq,seq] - Division,
/
- mod[,s,eq,seq] - Modulo,
%
- band[,s,eq,seq] - Bitwise And,
&
- bor[,s,eq,seq] - Bitwise Or,
&
- bxor[,s,eq,seq] - Bitwise Xor,
^
- lshift[,s,eq,seq] - Left shift,
<<
- rshift[,s,eq,seq] - Signed right shift,
>>
- rrshift[,s,eq,seq] - Unsigned right shift,
>>>
- lt[,s,eq,seq] - Less than,
<
- gt[,s,eq,seq] - Greater than,
>
- leq[,s,eq,seq] - Less than or equal,
<=
- geq[,s,eq,seq] - Greater than or equal
>=
- eq[,s,eq,seq] - Equals,
===
- neq[,s,eq,seq] - Not equals,
!==
- and[,s,eq,seq] - Boolean And,
&&
- or[,s,eq,seq] - Boolean Or,
||
- max[,s,eq,seq] - Maximum,
Math.max
- min[,s,eq,seq] - Minimum,
Math.min
Special Cases
There are a few corner cases that follow slightly different rules. These can be grouped using the following general categories:
Assignment
There are two assignment operators:
- assign
- assigns
op.assign(dest, src)
copies one array into another, while op.assigns(dest, val)
broadcasts a scalar to all elements of an array.
Nullary operators
Nullary operators only take on argument for the array they are assigning to, and don't have any variations. Currently there is only one of these:
- random - Sets each element of an array to a random scalar between 0 and 1,
Math.random()
Unary operators
Unary operators have one of two forms, they can be written as either:
op
Or:
op
The former version sets dest = |arg|, while in the latter the operation is applied in place. ndarray-ops exposes the following unary operators:
- not[,eq] - Boolean not,
!
- bnot[,eq] - Bitwise not,
~
- neg[,eq] - Negative,
-
- recip[,eq] - Reciprocal,
1.0/
- abs[,eq] - Absolute value,
Math.abs
- acos[,eq] - Inverse cosine,
Math.acos
- asin[,eq] - Inverse sine,
Math.asin
- atan[,eq] - Inverse tangent,
Math.atan
- ceil[,eq] - Ceiling,
Math.ceil
- cos[,eq] - Cosine,
Math.cos
- exp[,eq] - Exponent,
Math.exp
- floor[,eq] - Floor,
Math.floor
- log[,eq] - Logarithm,
Math.log
- round[,eq] - Round,
Math.round
- sin[,eq] - Sine,
Math.sin
- sqrt[,eq] - Square root,
Math.sqrt
- tan[,eq] - Tangent,
Math.tan
Non-symmetric binary operators
There are also a few non-symmetric binary operators. These operators have an extra suffix op
which flips the order of the arguments. There are only two of these:
- atan2[,s,eq,seq,op,sop,opeq,sopeq]
- pow[,s,eq,seq,op,sop,opeq,sopeq]
Map-reduce (aggregate) operators
Finally, there are aggregate operators that take an array as input and compute some aggregate result or summary. These functions don't have any special suffixes and all of them take a single array as input.
- equals - Check if two ndarrays are equal
- any - Check if any element of the array is truthy
- all - Checks if any element of the array is falsy
- sum - Sums all elements of the array
- prod - Multiplies all elements of the array
- norm2squared - Computes the squared L2 norm
- norm2 - Computes the L2 norm
- norminf - Computes the L-infinity norm
- norm1 - Computs the L1 norm
- sup - Max element in array
- inf - Min element in array
- argmin - Index of min element
- argmax - Index of max element
Credits
(c) 2013 Mikola Lysenko. MIT License