I need to count the number of elements greater than a certain value

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You can use the following basic syntax to count the number of elements greater than a specific value in a NumPy array:

import numpy as np

vals_greater_10 = (data > 10).sum()

This particular example will return the number of elements greater than 10 in the NumPy array called data.

The following example shows how to use this syntax in practice.

Example: Count Number of Elements Greater Than Value in NumPy Array

Suppose we have the following 2D NumPy array with 15 total elements:

import numpy as np

#create 2D NumPy array with 3 columns and 5 rows
data = np.matrix(np.arange(15).reshape((5, 3)))

#view NumPy array
print(data)

[[ 0  1  2]
 [ 3  4  5]
 [ 6  7  8]
 [ 9 10 11]
 [12 13 14]]

We can use the following syntax to count the total number of elements in the array with a value greater than 10:

#count number of values greater than 10 in NumPy matrix
vals_greater_10 = (data > 10).sum()

#view results
print(vals_greater_10)

4

From the output we can see that 4 values in the NumPy array are greater than 10.

If we manually look at the NumPy array we can confirm that four elements – 11, 12, 13, 14 – are indeed greater than 10.

To find the number of elements less than 10, we can use the less than ( < ) operator instead:

#count number of values less than 10 in NumPy matrix
vals_less_10 = (data < 10).sum()

#view results
print(vals_less_10)

10

From the output we can see that 10 values in the NumPy array are less than 10.

The following tutorials explain how to perform other common operations in Python: