Add term entry for NumPy .where() built-in function

content/numpy/concepts/built-in-functions/terms/where/where.md

@@ -0,0 +1,79 @@
+---
+Title: '.where()'
+Description: 'Returns elements from arrays depending on a condition.'
+Subjects:
+  - 'Computer Science'
+  - 'Data Science'
+Tags:
+  - 'Arrays'
+  - 'Functions'
+  - 'Numpy'
+CatalogContent:
+  - 'learn-python-3'
+  - 'paths/data-science'
+---
+
+The **`.where()`** function is a built-in method in NumPy used for conditional selection of elements in arrays. It returns elements based on a condition:
+
+- When only the condition is provided, `.where()` returns the indices where the condition is `True`.
+- When all three arguments are provided i.e. condition, x, and y, it returns an array where elements from `x` are selected where the condition is `True`, and elements from `y` are selected where the condition is `False`.
+
+## Syntax
+
+```pseudo
+numpy.where(condition[, x, y])
+```
+
+**Parameters:**
+
+- `condition`: A boolean array or condition expression. Elements that evaluate to `True` will take values from `x`, and elements that evaluate to `False` will take values from `y`.
+- `x` (optional): The array or value to be selected when the condition is `True`.
+- `y` (optional): The array or value to be selected when the condition is `False`.
+
+**Return value:**
+
+- When all three arguments are provided, it returns an array with elements taken from `x` where the condition is `True`, and elements taken from `y` where the condition is `False`.
+- When only the condition is provided, it returns the indices where the condition is `True`.
+
+## Example
+
+The following example demonstrates how to use the `.where()` function with the parameters:
+
+```py
+import numpy as np
+
+arr = np.array([10, 15, 20, 25, 30])
+
+# Get the indices where elements are greater than 20
+indices = np.where(arr > 20)
+print(indices)
+
+# Use condition to select values from two arrays
+result = np.where(arr > 20, "big", "small")
+print(result)
+```
+
+This example results in the following output:
+
+```shell
+(array([3, 4]),)
+['small' 'small' 'small' 'big' 'big']
+```
+
+## Codebyte example
+
+Run the following codebyte example better to understand the `.where()` function:
+
+```codebyte/python
+import numpy as np
+
+arr = np.array([1, 2, 3, 4, 5])
+
+# Replace elements less than 3 with 0, others with 1
+result = np.where(arr < 3, 0, 1)
+
+print("Original array:", arr)
+print("Transformed array:", result)
+```
+
+In this example, elements less than `3` are replaced with `0`, and others with `1`.