• matrix.rb

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# Vector

The `Vector` class represents a mathematical vector, which is useful in its own right, and also constitutes a row or column of a Matrix.

## Method Catalogue¶ ↑

To create a Vector:

• ` Vector.[](*array) `

• ` Vector.elements(array, copy = true) `

To access elements:

• ` [](i) `

To enumerate the elements:

• ` #each2(v) `

• ` #collect2(v) `

Vector arithmetic:

• ` *(x) "is matrix or number" `

• ` +(v) `

• ` -(v) `

Vector functions:

• ` #inner_product(v) `

• ` #collect `

• ` #map `

• ` #map2(v) `

• ` #r `

• ` #size `

Conversion to other data types:

• ` #covector `

• ` #to_a `

• ` #coerce(other) `

String representations:

• ` #to_s `

• ` #inspect `

### Public Class Methods

[](*array) click to toggle source

Creates a Vector from a list of elements.

`Vector[7, 4, ...]`
```
# File matrix.rb, line 999
def Vector.[](*array)
new(:init_elements, array, copy = false)
end
```
elements(array, copy = true) click to toggle source

Creates a vector from an Array. The optional second argument specifies whether the array itself or a copy is used internally.

```
# File matrix.rb, line 1007
def Vector.elements(array, copy = true)
new(:init_elements, array, copy)
end
```
new(method, array, copy) click to toggle source

For internal use.

```
# File matrix.rb, line 1014
def initialize(method, array, copy)
self.send(method, array, copy)
end
```

### Public Instance Methods

*(x) click to toggle source

Multiplies the vector by `x`, where `x` is a number or another vector.

```
# File matrix.rb, line 1114
def *(x)
case x
when Numeric
els = @elements.collect{|e| e * x}
Vector.elements(els, false)
when Matrix
Matrix.column_vector(self) * x
else
s, x = x.coerce(self)
s * x
end
end
```
+(v) click to toggle source

```
# File matrix.rb, line 1130
def +(v)
case v
when Vector
Vector.Raise ErrDimensionMismatch if size != v.size
els = collect2(v) {
|v1, v2|
v1 + v2
}
Vector.elements(els, false)
when Matrix
Matrix.column_vector(self) + v
else
s, x = v.coerce(self)
s + x
end
end
```
-(v) click to toggle source

Vector subtraction.

```
# File matrix.rb, line 1150
def -(v)
case v
when Vector
Vector.Raise ErrDimensionMismatch if size != v.size
els = collect2(v) {
|v1, v2|
v1 - v2
}
Vector.elements(els, false)
when Matrix
Matrix.column_vector(self) - v
else
s, x = v.coerce(self)
s - x
end
end
```
==(other) click to toggle source

Returns `true` iff the two vectors have the same elements in the same order.

```
# File matrix.rb, line 1079
def ==(other)
return false unless Vector === other

other.compare_by(@elements)
end
```
Also aliased as: eql?
[](i) click to toggle source

Returns element number `i` (starting at zero) of the vector.

```
# File matrix.rb, line 1034
def [](i)
@elements[i]
end
```
clone() click to toggle source

Return a copy of the vector.

```
# File matrix.rb, line 1096
def clone
Vector.elements(@elements)
end
```
coerce(other) click to toggle source

FIXME: describe #coerce.

```
# File matrix.rb, line 1242
def coerce(other)
case other
when Numeric
return Scalar.new(other), self
else
raise TypeError, "#{self.class} can't be coerced into #{other.class}"
end
end
```
collect() click to toggle source

Like Array#collect.

```
# File matrix.rb, line 1189
def collect # :yield: e
els = @elements.collect {
|v|
yield v
}
Vector.elements(els, false)
end
```
Also aliased as: map
collect2(v) click to toggle source

Collects (as in Enumerable#collect) over the elements of this vector and `v` in conjunction.

```
# File matrix.rb, line 1064
def collect2(v) # :yield: e1, e2
Vector.Raise ErrDimensionMismatch if size != v.size
(0 .. size - 1).collect do
|i|
yield @elements[i], v[i]
end
end
```
compare_by(elements) click to toggle source

For internal use.

```
# File matrix.rb, line 1089
def compare_by(elements)
@elements == elements
end
```
covector() click to toggle source

Creates a single-row matrix from this vector.

```
# File matrix.rb, line 1228
def covector
Matrix.row_vector(self)
end
```
each2(v) click to toggle source

Iterate over the elements of this vector and `v` in conjunction.

```
# File matrix.rb, line 1052
def each2(v) # :yield: e1, e2
Vector.Raise ErrDimensionMismatch if size != v.size
0.upto(size - 1) do
|i|
yield @elements[i], v[i]
end
end
```
eql?(other) click to toggle source
Alias for: ==
hash() click to toggle source

Return a hash-code for the vector.

```
# File matrix.rb, line 1103
def hash
@elements.hash
end
```
init_elements(array, copy) click to toggle source

For internal use.

```
# File matrix.rb, line 1021
def init_elements(array, copy)
if copy
@elements = array.dup
else
@elements = array
end
end
```
inner_product(v) click to toggle source

Returns the inner product of this vector with the other.

```Vector[4,7].inner_product Vector[10,1]  => 47
```
```
# File matrix.rb, line 1175
def inner_product(v)
Vector.Raise ErrDimensionMismatch if size != v.size

p = 0
each2(v) {
|v1, v2|
p += v1 * v2
}
p
end
```
inspect() click to toggle source

Overrides Object#inspect

```
# File matrix.rb, line 1265
def inspect
str = "Vector"+@elements.inspect
end
```
map() click to toggle source
Alias for: collect
map2(v) click to toggle source

Like #collect2, but returns a Vector instead of an Array.

```
# File matrix.rb, line 1201
def map2(v) # :yield: e1, e2
els = collect2(v) {
|v1, v2|
yield v1, v2
}
Vector.elements(els, false)
end
```
r() click to toggle source

Returns the modulus (Pythagorean distance) of the vector.

`Vector[5,8,2].r => 9.643650761`
```
# File matrix.rb, line 1213
def r
v = 0
for e in @elements
v += e*e
end
return Math.sqrt(v)
end
```
size() click to toggle source

Returns the number of elements in the vector.

```
# File matrix.rb, line 1041
def size
@elements.size
end
```
to_a() click to toggle source

Returns the elements of the vector in an array.

```
# File matrix.rb, line 1235
def to_a
@elements.dup
end
```
to_s() click to toggle source

Overrides Object#to_s

```
# File matrix.rb, line 1258
def to_s
"Vector[" + @elements.join(", ") + "]"
end
```

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