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# General Concepts

General Concepts of Sequence Models

### 👩‍🏫 Notation

In the context of text processing (e.g: Natural Language Processing NLP)
 Symbol Description \$\$X^{}\$\$ The `t`th word in the input sequence \$\$Y^{}\$\$ The `t`th word in the output sequence \$\$X^{(i)}\$\$ The `t`th word in the `i`th input sequence \$\$Y^{(i)}\$\$ The `t`th word in the `i`th output sequence \$\$T^{(i)}_x\$\$ The length of the `i`th input sequence \$\$T^{(i)}_y\$\$ The length of the `i`th output sequence

### 🚀 One Hot Encoding

A way to represent words so we can treat with them easily

#### 🔎 Example

Let's say that we have a dictionary that consists of 10 words (🤭) and the words of the dictionary are:
• Car, Pen, Girl, Berry, Apple, Likes, The, And, Boy, Book.
Our \$\$X^{(i)}\$\$ is: The Girl Likes Apple And Berry
So we can represent this sequence like the following 👀
Car -0)0 ⌉ ⌈ 0 ⌉ ⌈ 0 ⌉ ⌈ 0 ⌉ ⌈ 0 ⌉ ⌈ 0
Pen -1) | 0 | | 0 | | 0 | | 0 | | 0 | | 0 |
Girl -2) | 0 | | 1 | | 0 | | 0 | | 0 | | 0 |
Berry -3) | 0 | | 0 | | 0 | | 0 | | 0 | | 1 |
Apple -4) | 0 | | 0 | | 0 | | 1 | | 0 | | 0 |
Likes -5) | 0 | | 0 | | 1 | | 0 | | 0 | | 0 |
The -6) | 1 | | 0 | | 0 | | 0 | | 0 | | 0 |
And -7) | 0 | | 0 | | 0 | | 0 | | 1 | | 0 |
Boy -8) | 0 | | 0 | | 0 | | 0 | | 0 | | 0 |
Book -9)0 ⌋ ⌊ 0 ⌋ ⌊ 0 ⌋ ⌊ 0 ⌋ ⌊ 0 ⌋ ⌊ 0
By representing sequences in this way we can feed out data to neural networks ✨