# How to Calculate Mean Across the Row or Column in a NumPy Array

Let’s see how we can calculate the mean across the row or column in a NumPy array using the `mean()` function.

Suppose we’re operating on the following NumPy array.

``````arr = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
``````

## 1. Calculating the Mean Across the Row

To calculate the mean across the row, we can use the `mean()` function along the axis `0`. This will give us the mean value of each row in the array.

``````mean_row = np.mean(arr, axis=0)
# [4. 5. 6.]
``````

## 2. Calculating the Mean Across the Column

To calculate the mean across the column, we can use the `mean()` function along the axis `1`. This will give us the mean value of each column in the array.

``````mean_column = np.mean(arr, axis=1)
# [2. 5. 8.]
``````

## 3. Calculating the Mean of the Entire Array

To calculate the mean of the entire array, we can use the `mean()` function without specifying any axis. This will give us the mean value of all the elements in the array.

``````mean_array = np.mean(arr)
# 5.0
``````