Reshape Data: Melt 融合不同的資料欄位_Intro to Pandas

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題目敘述

題目會給定一個pandas DataFrame作為輸入，要求我們以原有的資料表為基礎，融合不同的資料欄位。

以product作為index，融合quarter_1,quarter_2,quarter_3,quarter_4 這四個欄位，並且重新命名為quarter，並且將數值欄位名稱重新命名為sales。

題目的原文敘述

測試範例

Example 1:

Input:
+-------------+-----------+-----------+-----------+-----------+
| product     | quarter_1 | quarter_2 | quarter_3 | quarter_4 |
+-------------+-----------+-----------+-----------+-----------+
| Umbrella    | 417       | 224       | 379       | 611       |
| SleepingBag | 800       | 936       | 93        | 875       |
+-------------+-----------+-----------+-----------+-----------+
Output:
+-------------+-----------+-------+
| product     | quarter   | sales |
+-------------+-----------+-------+
| Umbrella    | quarter_1 | 417   |
| SleepingBag | quarter_1 | 800   |
| Umbrella    | quarter_2 | 224   |
| SleepingBag | quarter_2 | 936   |
| Umbrella    | quarter_3 | 379   |
| SleepingBag | quarter_3 | 93    |
| Umbrella    | quarter_4 | 611   |
| SleepingBag | quarter_4 | 875   |
+-------------+-----------+-------+
Explanation:
The DataFrame is reshaped from wide to long format. Each row represents the sales of a product in a quarter.

以product作為index，融合quarter_1,quarter_2,quarter_3,quarter_4 這四個欄位，並且重新命名為quarter，
並且將數值欄位名稱重新命名為sales。

演算法