Data is recorded facts, observations, or measurements that can be processed and acted on. Sights, sounds, temperatures, and transaction records all count. For AI, data is like fuel: an algorithm cannot make useful decisions if its inputs are missing, unsuitable, or poorly represented. section 1.1 section 1.3
Data can take different forms:
- Quantitative data records numerical measurements or counts, such as temperature or age in days. section 1.3
- Qualitative data records observations or judgments, such as a smell or a movie review. Its meaning may depend on the observer. section 1.3
From a reading to a decision
A patient's temperature of 38°C is data. Interpreting that reading as a fever produces information. Deciding to administer medication draws on that information and experience: knowledge. The same recorded fact can support different interpretations depending on the question and context. section 1.3 section 2.4
For machine learning, data is commonly arranged in a table: each row is an example and each column is a feature. Apartment listings, for instance, can pair location, room count, and garage access with monthly rent. Comparing listings reveals patterns that help estimate the rent of a new apartment. Larger, more complex datasets make collecting and understanding the right features especially important. section 8.1 section 8.7
Table 8.1 The diamond dataset
|
Carat |
Cut |
Color |
Clarity |
Depth |
Table |
Price |
X |
Y |
Z |
|
| 1 |
0.30 |
Good |
J |
SI1 |
64.0 |
55 |
339 |
4.25 |
4.28 |
2.73 |
| 2 |
0.41 |
Ideal |
I |
SI1 |
61.7 |
55 |
561 |
4.77 |
4.80 |
2.95 |
| 3 |
0.75 |
Very good |
D |
SI1 |
63.2 |
56 |
2,760 |
5.80 |
5.75 |
3.65 |
| 4 |
0.91 |
Fair |
H |
SI2 |
65.7 |
60 |
2,763 |
6.03 |
5.99 |
3.95 |
| 5 |
1.20 |
Fair |
F |
I1 |
64.6 |
56 |
2,809 |
6.73 |
6.66 |
4.33 |
| 6 |
1.31 |
Premium |
J |
SI2 |
59.7 |
59 |
3,697 |
7.06 |
7.01 |
4.20 |
| 7 |
1.50 |
Premium |
H |
I1 |
62.9 |
60 |
4,022 |
7.31 |
7.22 |
4.57 |
| 8 |
1.74 |
Very good |
H |
I1 |
63.2 |
55 |
4,677 |
7.62 |
7.59 |
4.80 |
| 9 |
1.96 |
Fair |
I |
I1 |
66.8 |
55 |
6,147 |
7.62 |
7.60 |
5.08 |
| 10 |
2.21 |
Premium |
H |
I1 |
62.2 |
58 |
6,535 |
8.31 |
8.27 |
5.16 |
The diamond dataset makes the table structure concrete: rows describe individual diamonds, while columns record features such as carat, cut, dimensions, and sale price. section 8.7
Choosing data is part of solving the problem, not just feeding an algorithm. First decide what question matters, then collect relevant data, understand what its fields mean, clean and format it, and test whether the resulting model helps. Results may send you back to revise the data. Even accurate measurements can mislead when selected in a biased way. section 8.6 section 1.3







