Knowing the index (x,y,z) of a specific element in a NumPy array can be helpful for visualizing the array, such as plotting a line or point at the location of the element. There are various methods to determine the index using NumPy. In this thread, we will discuss some methods of how we find the index of the specified element of an array.
1. Using "argpartition()" and "unravel_index()" :
One way to find the (x,y,z) index of the specified element in a NumPy array is to use the argpartition()
function. It takes two arguments: the array to be partitioned, and the index of the element we want to find. It returns the indices that would partition the array into the desired order. For example:
After finding indices, we then take the first 100 indices using slicing, and find the index of the last element in the resulting array using the unravel_index()
function.

unravel_index(indices, shape)
function that takes a flat index or an array of flat indices and returns the corresponding tuple of multidimensional indices.
This gives us the index of the 100th element in the array.
2. Using "argsort()" function:
 The
argsort()
function in NumPy is used to perform an indirect sort on an input array, which means it returns an array of indices that would sort the input array. It takes an array as input and returns an array of indices that would sort the input array along the specified axis.
For example, to find the index (x,y,z) of the 100th element is by using the argsort()
function.