# Advanced NumPy Exercises - Subtract the mean of each row from each element of a 3x3 array

## NumPy: Advanced Exercise-4 with Solution

Write a NumPy program to create a 3x3 array with random values and subtract the mean of each row from each element.

**Sample Solution:**

**Python Code:**

```
import numpy as np
# create a 3x3 array with random values
arr = np.random.rand(3, 3)
print("Original array elements:")
print(arr)
# subtract the mean of each row from each element
row_means = np.mean(arr, axis=1, keepdims=True)
print("\nMean of each row:")
print(row_means)
arr_subtracted = arr - row_means
print("\nSubtract the mean of each row from each element:")
print(arr_subtracted)
```

Sample Output:

Original array elements: [[0.61550214 0.59670368 0.5847669 ] [0.73449098 0.79990957 0.42938855] [0.811186 0.19465177 0.93097873]] Mean of each row: [[0.59899091] [0.65459637] [0.6456055 ]] Subtract the mean of each row from each element: [[ 0.01651124 -0.00228723 -0.01422401] [ 0.07989461 0.14531321 -0.22520782] [ 0.1655805 -0.45095373 0.28537323]]

**Explanation:**

In the above exercise -

arr = np.random.rand(3, 3): This line of code creates a 3x3 NumPy array arr with random values between 0 and 1 using the rand() function from the np.random module.

row_means = np.mean(arr, axis=1, keepdims=True): This line computes the mean of each row in arr using the mean() function from the NumPy module. The axis=1 argument specifies that we want to compute the means along the rows, and the keepdims=True argument ensures that the resulting array has the same shape as arr with a new axis for the means.

arr_subtracted = arr - row_means: This code subtracts the row means from each element in the corresponding row of arr to obtain a new array arr_subtracted.

**Python-Numpy Code Editor:**

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**Previous:** Find the sum of a 4x4 array containing random values.

**Next:** Subtract the mean of each column from each element of a 3x3 array.

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## Python: Tips of the Day

**Decapitalizes the first letter of a string:**

Example:

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Output:

pythonTips pYTHONTIPS

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