Update README.md

Signed-off-by: David Rotermund <54365609+davrot@users.noreply.github.com>

numpy/ravel_unravel/README.md

@@ -18,6 +18,35 @@ numpy.ravel_multi_index(multi_index, dims, mode='raise', order='C')
 
 > Converts a tuple of index arrays into an array of flat indices, applying boundary modes to the multi-index.
 
+```python
+import numpy as np
+
+idx = np.ravel_multi_index(([0, 1, 2], [0, 1, 1]), dims=(3, 2))
+print(idx)  # -> [0 3 5]
+
+a = np.zeros((3, 2))
+a.flat[idx] = 1
+print(a)
+print()
+
+a = np.zeros((3, 2))
+a.flat[idx] = np.arange(1, idx.shape[0] + 1)
+print(a)
+```
+
+Output:
+
+```python
+[[1. 0.]
+ [0. 1.]
+ [0. 1.]]
+
+[[1. 0.]
+ [0. 2.]
+ [0. 3.]]
+```
+
+
 ## [numpy.unravel_index](https://numpy.org/doc/stable/reference/generated/numpy.unravel_index.html)
 
 ```python