Indexing in Daru has grown more powerful. Here's a glimpse. Enjoy!

In [1]:

require 'daru'

Out[1]:

true

Categorical Index¶

A new class of index got added to Daru to handle indexing which can be categorical. This is basically how it works.

In [2]:

idx = Daru::CategoricalIndex.new [:a, 1, :a, 1, :c]

Out[2]:

#<Daru::CategoricalIndex(5): {a, 1, a, 1, c}>

In [3]:

dv = Daru::Vector.new 'a'..'e', index: idx

Out[3]:

Daru::Vector(5)
a	a
1	b
a	c
1	d
c	e

Get elements with single category.

In [4]:

dv[:a]

Out[4]:

Daru::Vector(2)
a	a
a	c

Retrive elements by multiple categories.

In [5]:

dv[:a, 1]

Out[5]:

Daru::Vector(4)
a	a
1	b
a	c
1	d

Get elements by position using #at.

In [6]:

dv.at 1

Out[6]:

"b"

You can get multiple element as a vector if you specify more than one position.

In [7]:

dv.at 0, 1, 2

Out[7]:

Daru::Vector(3)
a	a
1	b
a	c

Note: You can also use #[] to get elements by position only if that position is not a index.

Get elements by single position.

In [8]:

dv[3]

Out[8]:

"d"

Get elements by multiple positions.

In [9]:

dv[0, 3]

Out[9]:

Daru::Vector(2)
a	a
1	d

Change values at certain indexes using []=

In [10]:

dv[:a] = 20
dv

Out[10]:

Daru::Vector(5)
a	20
1	b
a	20
1	d
c	e

Change values at certain positions using at_set

In [11]:

dv.at_set [0, 1], 100
dv

Out[11]:

Daru::Vector(5)
a	100
1	100
a	20
1	d
c	e

Other index classes¶

Overall all Index classes API are improved. Everyclass respond to multiple indexes, positional index, give proper error messages, etc.

Here are few examples:

Index¶

In [12]:

idx = Daru::Index.new [:a, :b, :c, :d]

Out[12]:

#<Daru::Index(4): {a, b, c, d}>

In [13]:

dv = Daru::Vector.new 1..4, index: idx

Out[13]:

Daru::Vector(4)
a	1
b	2
c	3
d	4

Retrive values by index or positions.

Note: When the value is both a valid index and a valid position, it will be treated as index value.

In [14]:

dv[:a, :b]

Out[14]:

Daru::Vector(2)
a	1
b	2

Retive values by positions.

In [15]:

dv.at 0, 1

Out[15]:

Daru::Vector(2)
a	1
b	2

Set values by index or positions.

Note: When value is both a valid index and a valid position, it will be treated as index value.

In [16]:

dv[:a, :b] = 'x'
dv

Out[16]:

Daru::Vector(4)
a	x
b	x
c	3
d	4

Set values in vector by positions.

In [17]:

dv.at_set [0, 2], 'y'
dv

Out[17]:

Daru::Vector(4)
a	y
b	x
c	y
d	4

MultiIndex¶

In [18]:

idx = Daru::MultiIndex.from_tuples [
          [:a,:one,:bar],
          [:a,:one,:baz],
          [:a,:two,:bat],
          [:b,:one,:bar],
          [:b,:two,:baz],
        ]

Out[18]:

Daru::MultiIndex(5x3)
a	one	bar
	one	baz
	two	bat
b	one	bar
b	two	baz

In [19]:

dv = Daru::Vector.new 1..5, index: idx

Out[19]:

Daru::Vector(5)
a	one	bar	1
	one	baz	2
	two	bat	3
b	one	bar	4
b	two	baz	5

Retrive values by index or positions.

Note: When value is both a valid index or position then value will be treated as index rather position.

Partial Index

In [20]:

dv[:a]

Out[20]:

Daru::Vector(3)
one	bar	1
one	baz	2
two	bat	3

On mentioning complete index, one will get the value at that index

In [21]:

dv[:a, :one, :bar]

Out[21]:

Retrive values by positions

In [22]:

dv.at 0, 1, 2

Out[22]:

Daru::Vector(3)
a	one	bar	1
	one	baz	2
	two	bat	3

Assign values by index or positions

In [23]:

dv[:a, :one] = 'x'
dv

Out[23]:

Daru::Vector(5)
a	one	bar	x
	one	baz	x
	two	bat	3
b	one	bar	4
b	two	baz	5

Assign values by positions

In [24]:

dv.at_set [0, 1, 2], 'z'
dv

Out[24]:

Daru::Vector(5)
a	one	bar	z
	one	baz	z
	two	bat	z
b	one	bar	4
b	two	baz	5