Get index of max element numpy ndarray Remember, basic indexing in numpy returns views, not copies, impacting the original array. Step-by-step examples included! numpy. Apply np. argwhere(a) [source] # Find the indices of array elements that are non-zero, grouped by element. max would return an ndarray. argmax for full documentation. amax: Let’s create a 1D numpy array from a list given below and find the maximum values and its index Find maximum value: Numpy find max index: To find the maximum value in the array, we can use numpy. Thank you very much for any help! My question is very similar to this one: How to get indices of N maximum values in a numpy array? But I would like to get the indices in the same order I find them. This function is particularly useful for identifying the position of the highest element in a dataset. mean(), np. max # method matrix. By default, the index is into the flattened array, otherwise along the specified axis. ndarray’ object has no attribute ‘index’ is an attribute error which indicates that there is no index method or attribute available to use in Numpy array. ndarray' object has no attribute ' Mar 8, 2024 · The numpy. But with a NumPy array, when I try to do: decoding. Hence, you should The first array returned contains the indices along axis 1 in the original array, the second array contains the indices along axis 2. in matlab [val,I]=max(v) , val = "maximum value" and I = "index number" witch v is a 1x12 double The row index is just [0, 1, 2] and the column index specifies the element to choose for the corresponding row, here [0, 1, 0]. Parameters: aarray_like Input data. max Notes This is the same as ndarray. Parameters: *argsArguments (variable number and type) none: in this case, the method only works for arrays with one element (a. Utilizing argmax () with Multi-dimensional Arrays Consider a two-dimensional array. See how it works: maximum_element = numpy. Using max () max () function finds the largest value and index () returns numpy. After finding the max, I used peakIndex = numpy. roll # numpy. May 24, 2014 · I have a numpy. where(myArray==max) to find the peak's inde Nov 6, 2024 · In the realm of data manipulations with Python, particularly using NumPy, one common task is to identify the indices of maximum elements within a multidimensional array. max # numpy. mat will contain MATLAB matrices (always 2d or higher), cells and structures. 3 Which method is used to get the index along a particular axis in a multidimensional array, and How? 3. NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme. See also max alias of this function ndarray. argmax() identifies the maximum value 90 in the array and returns its index, which is 2. Compute an array where the subarrays contain index values 0, 1, … varying only along the corresponding axis. Here, s k are integers which specify the strides of the Mar 26, 2022 · x = np. Learn more about NumPy at What is NumPy, and if you have comments or suggestions, please reach out! How to import NumPy # The NumPy library contains multidimensional array data structures, such as the homogeneous, N-dimensional ndarray, and a large library of functions that operate efficiently on these data structures. max() method in NumPy stands as a powerful tool for extracting the maximum values from arrays, regardless of their complexity. argmin, argmax amin The minimum value along a given axis. Using these indices with slicing, we can extract the top n largest elements efficiently. sort Inplace sort. Feb 26, 2024 · Here, we calculated the maximum across the color channels using np. This array will have shape (N, a. Indices are grouped by element. To group the indices by element, rather than dimension, use argwhere, which returns a row for each Apr 5, 2023 · I have this matlab code which aims to find the index with max value across each column of a 2-dimensional matrix. An example with a 3-dimensional array is provided. argmax # method ndarray. An array is created using numpy. Nov 6, 2024 · In this post, we will delve into the most effective methods for locating the indices of maximum elements in a 2-dimensional NumPy array. max(a, axis=None, out=None, keepdims=<no value>, initial=<no value>, where=<no value>) [source] # Return the maximum of an array or maximum along an axis. Learn how to access elements using square brackets, pair of indices, or combining indexing with :, enabling easy selection of rows, columns, and higher dimensions. Using both together the task can be solved using advanced indexing: This tutorial explains how to use the NumPy argmax() function in Python to find the indices of the maximum element in an array. An associated data-type object describes the format of each element in the array (its byte-order, how many bytes it occupies in memory, whether it is an integer, a floating point number, or numpy. ndarray. Input array. I would like a similar thing, but returning the indexes of the N maximum values. ndarray. In a strided scheme, the N-dimensional index corresponds to the offset (in bytes): from the beginning of the memory block associated with the array. dtypedtype, optional Data type of the result. Returns: index_array(N, a. argpartition Indirect partial sort. min () and max () functions of numpy. unravel_index Convert a flat index into an index tuple. By default, flattened input is used. Instead of directly returning the sorted array, argsort () returns the indices that would sort the array. Compare two arrays and return a new array containing the element-wise maxima. If this is a tuple of ints, the maximum is selected over multiple axes Dec 31, 2024 · Learn how to find the index of the maximum value in a Python array using methods like `index()`, loops, and NumPy's `argmax()`. Jan 20, 2024 · NumPy allows you to calculate the sum, average, maximum, and minimum of an array (ndarray) using functions such as np. int_type: this argument is interpreted as a flat index into May 30, 2019 · I expect the output to be the name of the image, but I instead get TypeError: only integer scalar arrays can be converted to a scalar index that is because i is of type numpy. amax which only provides a Jan 31, 2021 · NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme. Use the axis parameter to get the index of the Jan 18, 2025 · In this introduction to NumPy, you'll learn how to find extreme values using the max() and maximum() functions. Examples This is not a duplicate of How to get the index of a maximum element in a NumPy array along one axis. Overview of the Problem Consider the case where you have a 2D numpy. It calculates the index of the maximum element of the array across all axis, not along a given axis as the OP asks: it is wrong. Create a function that returns the global index of the maximum element in a flattened 2D array. The np. It’s allows us to store and manipulate large amounts of data efficiently. For finding an element stopping after the first match in a NumPy array use an iterator (ndenumerate). In this example, we extract the 1 largest value from a NumPy array. The maximum of a 2D array is not the same as the maximum along some axes. See also compress Take elements using a boolean mask ndarray. where(condition, [x, y, ]/) # Return elements chosen from x or y depending on condition. The Numpy argmax () function is used to find the index of the maximum value in an array along a specified axis. argmax(axis=None, out=None, *, keepdims=False) # Return indices of the maximum values along the given axis. numpy. Jun 18, 2020 · in the python, I'm trying to find the max value of a numpy array with its index number. Parameters: dimensionssequence of ints The shape of the grid. sparseboolean, optional Return a numpy. The type of items in the array is specified by a separate data-type object (dtype), one of which is NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme. ndarray () provides the minimum and maximum values along the specified axis. For Python lists see Find the most common element in a list and Find the item with maximum occurrences in a list. Jun 10, 2017 · NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme. [10,5,19,56,87,96,74,15,50,12,98] import numpy as np NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme. JAX’s behavior differs from NumPy in the case of out-of-bound indices; see the mode parameter below. max next numpy. Master advanced slicing and indexing techniques with numpy. Parameters: aarray_like Input array. max(axis=None, out=None, *, keepdims=<no value>, initial=<no value>, where=<no value>) # Return the maximum along a given axis. argmax() without specifying an axis to find the overall maximum index. And there are nd numeric or string arrays. indices(dimensions, dtype=<class 'int'>, sparse=False) [source] # Return an array representing the indices of a grid. numpy. Dec 31, 2024 · In this tutorial, I explained how to find the index of the maximum value in an array using Python, and there are multiple ways to accomplish it. You may have to work through several levels to get at the Index the same ndarray multiple times efficiently # It must be kept in mind that basic indexing produces views and advanced indexing produces copies, which are computationally less efficient. max(arr, 0) maximum_element = numpy. roll(a, shift, axis=None) [source] # Roll array elements along a given axis. shiftint or tuple of ints The number of places by which elements are shifted. Indexing on ndarrays — NumPy v1. In a strided scheme, the N-dimensional index (n0, n1,, nN − 1) corresponds to the offset (in Notice that the initial value is used as one of the elements for which the minimum is determined, unlike for the default argument Python’s max function, which is only used for empty iterables. argmax () function returns indices of the max element of the array in a particular axis. While comparing, one of the elements of two arrays is a NaN, then that element is returned as NaN. max(axis=None, out=None, keepdims=False, initial=<no value>, where=True) # Return the maximum along a given axis. The values in a are always tested and returned in row-major, C-style order. index(i) I get: AttributeError: 'numpy. Array objects # NumPy provides an N-dimensional array type, the ndarray, which describes a collection of “items” of the same type. 4 How do you get multiple indexes for redundant maximum or minimum values? 4 Conclusion 5 Index the same ndarray multiple times efficiently # It must be kept in mind that basic indexing produces views and advanced indexing produces copies, which are computationally less efficient. where # numpy. The items can be indexed using for example N integers. Usage The `argmax ()` function is used when you need to determine the index of the maximum element along a specific axis of an array. [~, indk] = max(R2) I would like to apply this in python but cannot seem to fi If you have a preference just order the inputs to max accordingly. To group the indices by element, rather than dimension, use argwhere, which returns a row for each Nov 28, 2021 · ‘numpy. The NumPy library contains multidimensional array data structures, such as the homogeneous, N-dimensional ndarray, and a large library of functions that operate efficiently on these data structures. nonzero(a) [source] # Return the indices of the elements that are non-zero. Jul 26, 2025 · ndarray is a short form for N-dimensional array which is a important component of NumPy. Hence, you should Sep 27, 2025 · The numpy. Jan 19, 2025 · 0 This question already has answers here: Find the column index by the maximum value of row in numpy (1 answer) How to get the index of a maximum element in a NumPy array along one axis (6 answers) The NumPy library contains multidimensional array data structures, such as the homogeneous, N-dimensional ndarray, and a large library of functions that operate efficiently on these data structures. 2 numpy. How to get the index of the maximum value in a Numpy array? NumPy's `argmax ()` function is used in array computation and analysis to find the index of the maximum value within an array. Hence, you should numpy. These functions allow you to specify the axis argument to obtain results for each column (column-wise) or each row (row-wise). Conclusion The ndarray. 2 What is the difference between the index () method and the where the () method of NumPy? 3. max, but returns a matrix object where ndarray. For instance, if I have an arr The first array returned contains the indices along axis 1 in the original array, the second array contains the indices along axis 2. If I want to find both max and min, I have to call both functions, which requires passing over t 9 argpartition (a, k) function in numpy rearranges indices of input array a around the kth smallest element, so that all indices of smaller elements end up to the left, and all indices of bigger elements end up to the right. Jul 23, 2021 · One more doubt: lets say if there are more than one elements in the array have same max val then what will this output? I tried some sample data and it is outputing the first index of the max value. If this is a tuple of ints, the maximum is selected over multiple axes Aug 2, 2011 · NumPy proposes a way to get the index of the maximum value of an array via np. Sep 23, 2024 · Python NumPy maximum() or max() function is used to get the maximum value (greatest value) of a given array, or compare the two arrays element-wise and return the maximum values. Structured datatypes are implemented in numpy to have base type numpy. nanmax () returns the maximum value of the array ignoring nans. argmax. I've tried np. Here, s k are integers which specify the strides of the Jul 4, 2025 · Finding the index of the maximum item in a Python list means identifying the position where the largest value occurs. ndarray and I want to know the index of it's max entry. Here, are integers which specify the strides of the array. 1 What exactly does a NumPy ndarray represent? 3. Refer to numpy. Mar 1, 2024 · Finding the indices of the top N maximum values in a NumPy array is a fundamental task that can be performed efficiently using various methods. org Jul 23, 2025 · Example 1: Get index positions of a given value Here, we find all the indexes of 3 and the index of the first occurrence of 3, we get an array as output and it shows all the indexes where 3 is present. index(). index(x) returns the smallest i such that i is the index of the first occurrence of x in the list. take(a, indices, axis=None, out=None, mode=None, unique_indices=False, indices_are_sorted=False, fill_value=None) [source] # Take elements from an array. In this blog, we will explore the fundamental concepts, usage methods, common practices, and best practices related to the `max` function of NumPy arrays. Whether working with simple NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme. This has the advantage that it runs in linear time. Jul 23, 2025 · Example 1: In this example, the NumPy package is imported. How to use numpy index of max? You may need to find the index of the max value in the Numpy array. fmax Notice that the initial value is used as one of the elements for which the minimum is determined, unlike for the default argument Python’s max function, which is only used for empty iterables. Whether you prefer using built-in functions like max() and index(), using of the numpy library with argmax() function, or using list comprehensions. g. item # method ndarray. If provided, the result will be inserted into this array. argwhere # numpy. See full list on statology. int_type: this argument is interpreted as a flat index into numpy. amax() The numpy. Oct 16, 2025 · The `max` function in NumPy provides a simple yet powerful way to obtain the largest element in an array, and it can be used in various scenarios with different configurations. One can safely assume that the index() function in Python is implemented so that it stops after finding the first match, and this results in an optimal average performance. If this is a tuple of ints, the maximum is selected over multiple axes A segment of memory is inherently 1-dimensional, and there are many different schemes for arranging the items of an N -dimensional array in a 1-dimensional block. Not needing to sort all elements saves time: argpartition takes O (n) time, while argsort takes O (n log n) time. item(*args) # Copy an element of an array to a standard Python scalar and return it. unravel_index() function converts the flattened index back to a coordinate in the 2D space of the image. If one of the elements being compared is a NaN, then that element is returned. This iterates over matching 1d slices oriented along the specified axis in the index and data arrays, and uses the former to look up values in the latter. Learn more about NumPy at What is NumPy, and if you have comments or suggestions, please reach out! How to import NumPy # Jan 11, 2009 · l. axisNone or int or tuple of ints, optional Axis or axes along which to operate. Nov 11, 2015 · find the maximum value and its index in an numpy array Asked 10 years ago Modified 10 years ago Viewed 16k times See also ndarray. All ndarrays are homogeneous: every item takes up the same size block of memory, and all blocks are interpreted in exactly the same way. If both elements are NaNs then the first Mar 27, 2024 · NumPy argmax() in Python is used to return the indices of the max elements of the given array along with the specified axis. amax( ) function and pass the array as function to it. Understanding these methods is crucial for data analysis and manipulation, especially when working with large datasets in Python. argmax(array, axis = None, out = None) Parameters : array : Input array to work on axis : [int, optional]Along a specified axis like 0 or 1 out : [array optional]Provides a feature to insert output to the out array and it should be of appropriate shape and dtype Return : Array of numpy. In this tutorial, we will look at how to get the index of the max value in a Numpy array with the help of some examples. All elements in an ndarray must be of same type making it a homogeneous array. matrix. take equivalent method take_along_axis Take elements by matching the array and the index arrays Partitioning an array arr with index i rearranges the elements such that the element at index i is the ith greatest, while those on the left are greater and on the right are lesser. size == 1), which element is copied into a standard Python scalar object and returned. To group the indices by element, rather than dimension, use argwhere, which returns a row for each If you have a preference just order the inputs to max accordingly. Apr 14, 2021 · Learn how to use NumPy’s argmax () function to find the index position of the maximum value in arrays, essential for locating peaks and extreme values in data analysis. take_along_axis Apply index_array from argsort to an array as if by calling sort. void by default, but it is possible to interpret other numpy types as structured types using the (base_dtype, dtype) form of dtype specification described in Data Type Objects. Jun 23, 2016 · Without looking at your errors in detail I can point out some pitfalls. An associated data-type object describes the format of each element in the array (its byte-order, how many bytes it occupies in memory, whether it is an integer, a floating point number, or See also sort Describes sorting algorithms used. Jul 2, 2018 · First of all, index is a list method. For example, in a list like [2, 4, 6, 1, 8, 5, 3], the maximum value is 8, which is located at index 4. The . Elements that roll beyond the last position are re-introduced at the first. This error occurs when we try to find the index of a particular element in a Numpy array using the index method. argmax() method in NumPy is highly versatile, perfect for finding maxima in arrays or datasets. Notice that this isn’t the same as Python’s default argument. JAX implementation of numpy. Getting the first index of an elements in a NumPy array To Get the first index of an elements in a NumPy array, you can use numpy. Index the same ndarray multiple times efficiently # It must be kept in mind that basic indexing produces views and advanced indexing produces copies, which are computationally less efficient. maximum # numpy. argmax, argmin amax The maximum value along a given axis. amax() function is one of the simplest ways to find the maximum value in a NumPy array. This demonstrates how to get the index of the max value in a NumPy array. Syntax : numpy. It is particularly useful for tasks that require identifying the position of the highest value in data structures, such as arrays or matrices. If this is a tuple of ints, the maximum is selected over multiple axes Nov 8, 2024 · In this example, np. Notice that the initial value is used as one of the elements for which the minimum is determined, unlike for the default argument Python’s max function, which is only used for empty iterables. ndim attributes. May 28, 2025 · Explore the depths of NumPy's argmax() function – your gateway to efficiently locating the position of maximum elements in arrays. This function simplifies the process of finding the largest number among elements and is widely employed in mathematical and scientific computations where efficiency and numpy. There are object arrays (dtype=object). Hence, you should take care to use basic indexing wherever possible instead of advanced indexing. ndarray’ object has no attribute ‘index’ . take_along_axis(arr, indices, axis=-1) [source] # Take values from the input array by matching 1d index and data slices. sparseboolean, optional Return a See also ndarray. gather(). ndim) where N is the number of non-zero items. The partitions on the left and right are not necessarily sorted. take # jax. . Feb 21, 2024 · 3 FAQs 3. loadmat renders those in various ways. One fundamental operation is identifying the index of the maximum value in an array, which is critical for tasks like optimization, classification, and Aug 29, 2025 · Write a NumPy program to find the index of the maximum element along a specified axis using np. shape, . array () method which contains nan and other values and np. It is helpful in scenarios where The Numpy library in Python comes with a number of useful built-in functions to work with and manipulate Numpy arrays. Dec 29, 2024 · In this tutorial, you will learn how to use the NumPy argmax () function to find the index of the maximum element in arrays, with examples. Using this function gets the indices of maximum elements of single dimensions and multi-dimensional (row-wise or column-wise) of the given array. max(arr, 1) If we use 0 it will give us a list containing the maximum or minimum values from each column. Here we will get a See also ndarray. amax for full documentation. amin() does the same for the min value. It should be of the appropriate shape and dtype. This structure supports multiple dimensions which makes it ideal for handling complex datasets like those used in scientific computing or data analysis numpy. In a strided scheme, the N-dimensional index (n 0, n 1,, n N 1) corresponds to the offset (in bytes): n o f f s e t = ∑ k = 0 N 1 s k n k from the beginning of the memory block associated with the array. There are dictionaries that you have to index by name. max() and then used argmax() to find the index of the brightest pixel. sum(), np. argsort () function can be used to find the n-largest values in an array. max # method ndarray. max equivalent method previous numpy. These slices can be different lengths. Learn more about NumPy at What is NumPy, and if you have comments or suggestions, please reach out! How to import NumPy # May 23, 2023 · Suppose we are given a NumPy array with some values and we are given the specified item to search for. max(), and np. Method 1: Using numpy. indices # numpy. Further reading # Nicolas Rougier’s 100 NumPy exercises provide a good insight into how indexing is Oct 15, 2024 · If we try to apply the index() method on the NumPy array to find the element position, we get AttributeError: ‘numpy. ndim) ndarray Indices of elements that are non-zero. EDIT: Just to clarify, the idea is to leverage the numpy methods to reduce down to just two values and then use the key feature of the builtin max to arbitrate, since key is not supported by the numpy methods. The shape, datatype, and dimensions of the array can be found by . Returns a tuple of arrays, one for each dimension of a, containing the indices of the non-zero elements in that dimension. nonzero # numpy. Jun 21, 2020 · For example, There is a 2d Numpy matrix M: [[1,10,3], [4,15,6]] The max element except for those in M[:][1] is 6, and its position is (1,2). maximum(x1, x2, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature]) = <ufunc 'maximum'> # Element-wise maximum of array elements. expand_dims(index_array, axis) from argmin to an array as if by calling min. Moreover, if there is more than one maximum, it retrieves the indices of only the first maximum: this should be pointed out. lexsort Indirect stable sort with multiple keys. ndarray # class numpy. Mar 27, 2024 · How to get the index of the maximum (max) element of the list in Python? If you want to return the maximum element index position from the given list, you can use the max() to get the maximum value and use this value with index() method to get the index position of the maximum element. , rows or columns), in a NumPy array (ndarray) using various indexing. If a tuple, then axis must be a tuple of the same size, and each of the given axes is shifted by the Jul 26, 2019 · NumPy is flexible, and ndarray objects can accommodate any strided indexing scheme. amax() will find the max value in an array, and numpy. If both elements are NaNs then the first The Numpy library in Python comes with a number of useful built-in functions to work with and manipulate Numpy arrays. lax. max(axis=None, out=None) [source] # Return the maximum value along an axis. Returns the indices of the maximum values along an axis. min(). Here, s k are integers which specify the strides of the Jul 4, 2012 · How do I find the row or column which contains the array-wide maximum value in a 2d numpy array? The NumPy library contains multidimensional array data structures, such as the homogeneous, N-dimensional ndarray, and a large library of functions that operate efficiently on these data structures. The highest value in x[0] is therefore x[0, 1, 2]. Let’s explore the various approaches you can utilize to achieve this. This guide unveils five distinct methods to accomplish this for a 2D NumPy array, allowing you to extract maximum indices effectively based on your requirements. This includes finding the maximum element in an array or along a given axis of an array, as well as comparing two arrays to find the larger element in each index position. dtype, and . Here v is a numpy array and you need to do the following: jax. In a strided scheme, the N-dimensional index (n0, n1,, nN − 1) corresponds to the offset (in Jun 5, 2024 · Numpy. In Python we can get the index of a value in an array by using . An associated data-type object describes the format of each element in the array (its byte-order, how many bytes it occupies in memory, whether it is an integer, a floating point number, or Aug 13, 2021 · Output: maximum element in the array is: 81 minimum element in the array is: 2 Example 3: Now, if we want to find the maximum or minimum from the rows or the columns then we have to add 0 or 1. Is it the right behaviour? I have a one-dimensional array of the type numpy. The first array returned contains the indices along axis 1 in the original array, the second array contains the indices along axis 2. take_along_axis # numpy. This structure supports multiple dimensions which makes it ideal for handling complex datasets like those used in scientific computing or data analysis See also sort Describes sorting algorithms used. Parameters: See `amax` for complete descriptions See also amax, ndarray. Parameters: a (Array | ndarray numpy. Here, base_dtype is the desired underlying dtype, and fields and flags will be copied from dtype. The N-dimensional array (ndarray) # An ndarray is a (usually fixed-size) multidimensional container of items of the same type and size. take(), implemented in terms of jax. ndarray(shape, dtype=float, buffer=None, offset=0, strides=None, order=None) [source] # An array object represents a multidimensional, homogeneous array of fixed-size items. array([3, 4, 2, 1, 7, 8, 6, 5, 9]) I want to get an answer as array([9,8,7,6,5]) and their indices array([8,5,4,6,7]). Test the max-index finder on multi-dimensional arrays and verify that it correctly identifies the highest value. take_along_axis Apply np. expand_dims(index_array, axis) from argmax to an array as if by calling max. Mastering Argmax Calculations with NumPy Arrays NumPy, a cornerstone of Python’s numerical computing ecosystem, equips data scientists and researchers with powerful tools for efficient data analysis, particularly when handling large datasets. Feb 26, 2024 · In sum, the ndarray. ndarray Nov 18, 2024 · Introduction The max() function in the NumPy library is essential for data analysis, particularly when you need to quickly determine the maximum value in an array or along a specific axis in multi-dimensional arrays. How to get the index of the maximum value in a Numpy array? Feb 20, 2024 · For instance, if we have an array [3, 1, 5, 2, 4], we want to efficiently find the maximum value, which is 5 in this case. Learn more about NumPy at What is NumPy, and if you have comments or suggestions, please reach out! How to import NumPy # Feb 7, 2024 · This article explains how to get and set values, such as individual elements or subarrays (e. Spanning from basic one-dimensional arrays to sophisticated multidimensional or structured arrays, it adeptly accommodates a wide variety of data exploration and analysis requirements. Getting Started with NumPy Creating a NumPy array is numpy. The number of dimensions and items in an array is defined by its shape, which is a tuple of N non-negative integers that specify the sizes of each dimension. Here, s k are integers which specify the strides of the numpy. where () by passing arr == item, where arr is NumPy array and item is the value whose index to be found. array of data called f, I know the max value in it is f_max=max (f) but I would like to know the index in the array corresponding to the maximum value. So the answer is (1,2). Let’s explore different methods to efficiently find the index of the maximum element in a list.