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numpy.recarray¶ class numpy.recarray [source] ¶ Construct an ndarray that allows field access using attributes. Let us load pandas and numpy. 12, Mar 19. How to swap two columns of elements in a two-dimensional numpy array 17. However, this assumes that analysis is conducted in solvent conditions with high concentrations of buffer, as would be performed with UV-Vis detection. randint ( 10 , size = 6 ) # One-dimensional array x2 = np . the columns of `c`. So far we demonstrated examples of using Numpy where method. For NumPy >= 1.10.0, if a is an ndarray, then a view of a is returned; otherwise a new array is created. Question 2: How to swap two columns in a 2d numpy array? You can get the transposed matrix of the original two-dimensional array (matrix) with the Tattribute. Have another way to solve this solution? NumPy Basic Exercises, Practice and Solution: Write a NumPy program to find the number of rows and columns of a given matrix. First axis. But, we have already mentioned that we cannot use the Numpy. The matrix whose row will become the column of the new matrix and column will be the row of the new matrix. For a 2-D array, this is a standard matrix … How to swap columns of a given NumPy array? Change the order of columns in Pandas dataframe. This is a very elegant way to swap the columns: col1 = 0 col2 = 1 my_array.T[[col1, col2]] = my_array.T[[col2, col1]] Result: If I've misinterpreted your columns for rows, simply transform with .T - as C_Z_ answered above. Write a NumPy program to get the row numbers in given array where at least one item is larger than a specified value. A Computer Science portal for geeks. NumPy: Swap columns in a given array, There are two issues here. NumPy Matrix transpose() Python numpy module is mostly used to work with arrays in Python. Note: There are a lot of functions for changing the shapes of arrays in numpy flatten, ravel and also for rearranging the elements rot90, flip, fliplr, flipud etc. Note: Swap columns 1 and 2 in the array arr. Select Columns by Index from a 2D Numpy Array. For a 1 dimensional array is more like a list, there is no concept of rows and columns… Let’s apply numpy.square() function to rows and columns of the dataframe. Using NumPy's loadtxt method, The use of np.loadtxt is best illustrated using an example. Basics in Python for Machine Learning and Data Science. Python for beginners. ndarray.transpose (*axes) ¶ Returns a view of the array with axes transposed. asanyarray(a[, dtype, … n = np. NumPy Array Object Exercises, Practice and Solution: Write a NumPy program to access last two columns of a multidimensional columns. Changing kind of array¶ asarray(a[, dtype, order]) Convert the input to an array. What is the difficulty level of this exercise? So, we can print out array three sum, array three max, array three min and let's try array 3 mean. How to swap two columns in a 2d numpy array? My eigenvalues were in the first row and the corresponding eigenvector below it in the same column. For a 1-D array, this has no effect. Let’s implement with the help of NumPy: TensorFlow: An end-to-end platform for machine learning to easily build and deploy ML powered applications. import pandas as pd import numpy as np. Code in python. axis2 int. NumPy is a library for the Python programming language, adding support for large, multi-dimensional arrays and matrices, along with a large collection of high-level mathematical functions to operate on these arrays. If I've misinterpreted your columns for rows, simply transform with .T - as C_Z_ answered above. Calculating the sum of all columns of a 2D NumPy array. Python Programing. Find the number of rows and columns of a given matrix using NumPy, Python | Ways to add row/columns in numpy array, Calculating the sum of all columns of a 2D NumPy array, Calculate the sum of all columns in a 2D NumPy array. Swapping columns in a numpy array? In real-world python applications, we apply already present numpy functions to columns and rows in the dataframe. An example is [(x, int), (y, float)], where each entry in the array is a pair of (int, float). a[0,] is just the first row I want to sort by. Return to Content. It is the opposite of how it should work. numpy.swapaxes - This function interchanges the two axes of an array. random. For NumPy >= 1.10.0, if a is an ndarray, … Right now I am manually swapping rows and columns, but I would have expected numpy to have a nice function f(M, v) where M has n rows and columns, and v has n entries, so that f(M, v) updates M according to the index permutation v. Maybe I am just failing at searching the internet. Convert to numpy.ndarray and transpose with T; Convert to pandas.DataFrame and transpose with T; Transpose with built-in function zip() It is easier to use NumPy and pandas, but if you don't want to import NumPy or pandas just for transposition, you can use the zip() function. Arrays may have a data-types containing fields, analogous to columns in a spread sheet. To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. Unlike before, here we create a Pandas dataframe using two-dimensional NumPy array of size 8×3 and specify column names for the dataframe with the argument “columns”. Swap columns 1 and 2 in the array arr. Trying to switch the last two columns so it ends up like this: I've been doing this Though ending up with undesired What is the … Press J to jump to the feed. random . After that, we can swap the position of rows and columns to get the new matrix. The first is that the data you pass to your function apparently isn't a two-dimensional NumPy array -- at least this is What is the fastest way to swap two columns and the same rows of a 2D matrix? Having said that, it can get a little more complicated. For example let say that you want to compare rows which match on df1.columnA to df2.columnB but … ], [ 0., 1., 1., 1. For NumPy >= 1.10.0, if a is an ndarray, then a view of a is returned; otherwise a new array is created. PyTorch: Deep learning framework that accelerates the path from research prototyping to production deployment. My Solution. 5. To sort a dataframe in python pandas by two or more columns you can use the following code-df.sort_values(['q', 'w'], ascending=[True, False]) Ex- Let's create a DataFrame first, Creating a data frame: import pandas as pd. NumPy: Transpose ndarray (swap rows and columns, rearrange ; Python; How to transpose numpy array in python using transpose() function ... Transpose of a matrix is the interchanging of rows and columns. To convert a 1-D array into a 2D column vector, an additional dimension must be added. (That is, they cannot be dimension names.) Axis 0 is the direction along the rows. Python | Ways to add row/columns in numpy array. Let’s use these, Contents of the 2D Numpy Array nArr2D created above are, Multiple-scattering parameters of complex crystals and of imperfect hexagonal columns and plates can be well approximated by those of projected-area equivalent ice spheres, whereas perfect hexagonal crystals show values as much as 70% higher than those of spheres. NumPy: Array Object Exercise-150 with Solution. ], [ 0., 0., 0., -1.]]) 22, Aug 20. create dummy dataframe. Trust layer metadata propagation. (To change between column and row vectors, first cast the 1-D array into a matrix object.) How to rearrange columns of a 2D NumPy array using given index positions? Note: There are a lot of functions for changing the shapes of arrays in numpy flatten, ravel and also for rearranging the elements rot90, flip, fliplr, flipud etc. Returns a_swapped ndarray. Input array. Select Rows & Columns by Name or Index in Pandas DataFrame using [ ], loc & iloc. https://www.geeksforgeeks.org/how-to-swap-columns-of-a-given-numpy-array Python pandas: Apply a numpy functions row or column. Sample Solution: Python Code: import numpy as np my_array = … Essentially, the NumPy sum function sums up the elements of an array. Python program to convert a list to string, Reading and Writing to text files in Python, Different ways to create Pandas Dataframe, isupper(), islower(), lower(), upper() in Python and their applications, Python | Program to convert String to a List, Write Interview
Example 1: Swapping the column of an array. Nowadays, we don’t use the sort() method as it got removed in the 0.20.0 release. For NumPy versions after 1.10, a view of the swapped array is returned. Now, numpy arrays also have an interesting aggregation functions on them, such as sum, max, min and mean. 10, Aug 20. shuffle the columns of 2D numpy array to make the given row sorted. Python | Ways to add row/columns in numpy array. How to convert 1-D arrays as columns into a 2-D array in Python? Difficulty Level: L2. As with indexing, the array you get back when you index or slice a numpy array is a view of the original array. For a 2-D array, this is the usual matrix transpose. edit axis1 int. In that post on introduction to NumPy, I did a row-wise addition on a NumPy array. numpy.swapaxes¶ numpy.swapaxes (a, axis1, axis2) [source] ¶ Interchange two axes of an array. How to swap columns of a given NumPy array? Write a NumPy program to swap columns in a given array. The element at ith row and jth column in X will be placed at jth row and ith a: array_like. Therefore, we can use nested loops to implement this. If you want a list type object, get numpy.ndarray with the values attribute and convert it to list with the tolist method. On the similar logic we can sort a 2D Numpy array by a single row i.e. Difficulty Level: L2. The column used for size-exclusion HPLC was a Phenomenex BioSep-SEC-S2000 in [DIMENSIONS] format, which has a theoretical effective range between 200 and 1 kDa. For a 2-D array, To transpose NumPy array ndarray (swap rows and columns), use the T attribute (.T), the ndarray method transpose() and the numpy.transpose() function. Here is .gcd() method showing the greatest common divisor: Write a NumPy program to find elements within range from a given array of numbers. How to swap columns of a given NumPy array? The Tattribute returns a view of the original array, and changing one changes the other. So I want to sort a two-dimensional array column-wise by the first row in descending order. how to swap rows in 2d array in python. raw_data = {'name': pandas.DataFrame.swaplevel¶ DataFrame.swaplevel (i = - 2, j = - 1, axis = 0) [source] ¶ Swap levels … It is denoted as X' . Let’s understand by examples, Suppose we have a 2D Numpy array i.e. random . Crash course in Python for data science, machine learning. PROGRAM CODE: Se our new Python code below: 10, Aug 20. So, we can use plain logics behind this concept. Create an empty 2D Numpy Array / matrix and append rows or columns in python; Python Numpy : Select elements or indices by conditions from Numpy Array; Create Numpy Array of different shapes & initialize with identical values using numpy.full() in Python; How to Reverse a 1D & 2D numpy array using np.flip() and [] operator in Python This is a collection of exercises that have been collected in the numpy mailing list, on stack overflow and in the numpy documentation. 12, Mar 19. For earlier NumPy versions a view of a is returned only if the order of … Swap column contents - change column order df[['B', 'A']] = df[['A', 'B']]. random . Parameters a array_like. Contribute your code (and comments) through Disqus. Do not create a separate 2D array for the rotation, it rotates in the 2D array. NumPy-compatible sparse array library that integrates with Dask and SciPy's sparse linear algebra. Hence, there are many operations, (like flatten) , which when performed on a transposed array require a new array to be made. Pandas offers other ways of doing comparison. arr = np.arange(9).reshape(3,3) arr Solution The selected and specified labels must be in the same dimension and must be either category or group labels. How to swap two columns in a 2d numpy array? Cancel Unsubscribe. Posted on December 2, 2020 December 2, 2020 Numpy swap columns. numpy.swapaxes, To convert a 1-D array into a 2D column vector, an additional dimension must be added. It’s possible to also add up the rows or add up the columns of an array. Test your Python skills with w3resource's quiz. Another way is to use numpy. To select multiple columns use, ndArray[ : , start_index: end_index] It will return columns from start_index to end_index – 1. To select a single column use, ndArray[ : , column_index] It will return a complete column at given index. np.atleast2d(a).T achieves this, as does a[:, np.newaxis]. However, there are some differences. These fall under Intermediate to Advanced section of numpy. 14. Explaining row-major and column-major is beyond the scope of this post. 09, Jul 20. In particular, things get more complicated when you want to add new values specifically as new rows or columns. Here are some ways to swap the rows and columns of this two-dimensional list. Intersection means common elements in the given two arrays. If you want to append new values as a row (or a column), then you have to use the axis parameter of the NumPy append function. Q. Calculating the sum of all columns of a 2D NumPy array. 22, Aug 20. generate link and share the link here. Concatenate or join of two string column in pandas python is accomplished by cat() function. Swap Method (Python) Swaps the selected column(s) or rows with a specified column or row. Difficulty Level: L2. r2 is a slice of r. r2 = r [: 3,: 3] r2. 100 numpy exercises. Subscribe Subscribed Unsubscribe 1.9K. Lets say x = 0 & y =2 , and the input array is as below: a = [[4 3 1] [5 7 0] Stack Overflow Put the index as a whole: a[[x, y]] = a[[y, x]]. The function takes the following pa 1. numpy.shares_memory() — Nu… import pandas as pd import numpy as np pd.__version__ We will generate some data using NumPy’s random module and store it in a Pandas dataframe. Writing code in comment? Select Rows & Columns by Name or Index in Pandas DataFrame using [ ], loc & iloc. brightness_4 np.atleast2d(a).T achieves this, as does a[:, np.newaxis]. How to Remove columns in Numpy array that contains non-numeric values? Scala Programming Exercises, Practice, Solution. These fall under Intermediate to Advanced section of numpy. First construct a record dtype for the two fields, then read the relevant columns after skipping the first numpy.loadtxt ¶ numpy.loadtxt For example, usecols = … Strengthen your foundations with the Python Programming Foundation Course and learn the basics. The default, None, results in all columns being read. How to extract all values from a numpy array according to a specified range 15. Python's standard math library has great methods that make almost any basic math calculation a breeze. Return to Content. we can also concatenate or join numeric and string column. Indeed, when I was learning it, I felt the same that this is not how it should work. Python | Numpy numpy.ndarray.__truediv__(), Data Structures and Algorithms – Self Paced Course, Ad-Free Experience – GeeksforGeeks Premium, We use cookies to ensure you have the best browsing experience on our website. The goal of this collection is to offer a quick reference for both old and new users but also to provide a set of exercises for those who teach. How to swap two rows of elements in a two-dimensional numpy array 18. Next: Write a NumPy program to get the row numbers in given array where at least one item is larger than a specified value. Numpy, Pandas, data science January 1, 2021 Oceane Wilson. Experience. numpy swap multiple elements in an array. arange (0, 30, 2) # start at 0 count up by 2, stop before 30 n. ... Be careful with copying and modifying arrays in NumPy! For a 1-D array this has no effect, as a transposed vector is simply the same vector. By using our site, you
There are two very closely related ways to access array columns by name: recarrays and structured arrays. Previous: Write a NumPy program to find elements within range from a given array of numbers. The data are swapped together with the labels. Q. Stack arrays a and b vertically. how to swap rows in 2d array in python, How to swap xth and yth rows of the 2-D NumPy array? The numpy.loadtxt ¶ numpy.loadtxt For example, usecols = (1,4,5) will extract the 2nd, 5th and 6th columns. Output will be also a 2D array of integers with the needed transformations applied to sort the given row or column. Compare columns of 2 DataFrames without np.where. I have a numpy array containing a random spread of 1s and 0s. To transpose NumPy array ndarray (swap rows and columns), use the T attribute (.T), the ndarray method transpose() and the numpy.transpose() function. import numpy as np. Therefore, we can implement this with the help of Numpy as it has a method called transpose (). It is the same data, just accessed in a different order. (rows, columns) m. shape (2, 3) arange returns evenly spaced values within a given interval. Draw samples from a uniform distribution. Numpy Swap Columns. In this article, let’s discuss how to swap columns of a given NumPy array. arr = np.arange(9).reshape(3,3) arr Show Solution # Input arr = np.arange(9).reshape(3,3) arr # Solution arr[:, [1,0,2]] #> array([[1, 0, 2], #> [4, 3, 5], #> [7, 6, 8]]) 17. numpy.ndarray.transpose¶ ndarray.transpose (*axes) ¶ Returns a view of the array with axes transposed. Example 2: Swapping the column of an array with the user chooses. The time complexity of this approach is O(mn), Where m and n are the number of elements in arr1[] and arr2[]. But here is … Input. import modules. Loading... Unsubscribe from Knowledge Amplifier? The concept of rows and columns applies to Numpy Arrays only if the dimension is more than 1. Input array. Does not conjugate! Use the shape method to find the dimensions of the array. Swap columns 1 and 2 in the array arr. How to stack two arrays vertically? code. 09, Jul 20. For two dimensional arrays, we could do the same thing for each row or column. a = … How to define a function so that the scalar processing function can also process the numpy array 16. Concatenating two columns of the dataframe in pandas can be easily achieved by using simple ‘+’ operator. Swap the first & last columns of a matrix Knowledge Amplifier. Attention geek! The first column is divided by 1, the second column by 2, and the third by 3. Suppose you have a numpy array like this: array([[ 0., -1., 0., 0. For earlier NumPy versions a view of a is returned only if the order of … Then one of the readers of the post responded by saying that what I had done was a column-wise addition, not row-wise. a = a[::, a[0,].argsort()[::-1]] So how does this work? How to swap two rows in a 2d numpy … You can slice a numpy array is a similar way to slicing a list - except you can do it in more than one dimension. You can check if ndarray refers to data in the same memory with np.shares_memory(). numpy.ndarray.transpose¶ method. "Convert numpy 3d array to 2d array in python" is published by Panjeh. Right now I am manually swapping rows and columns, but I would have expected numpy to have a nice function f(M, v) where M has n rows and columns, and v has n entries, so that f(M, v) updates M according to the index permutation v. Maybe I am just failing at searching the internet. We'll use NumPy's random number generator, which we will seed with a set value in order to ensure that the same random arrays are generated each time this code is run: In [1]: import numpy as np np . Posted on December 2, 2020 December 2, 2020 See the following code. ], [ 0., 0., -1., 0. close, link Then, the new matrix is generated. Write a NumPy program to swap columns in a given array. It just takes the elements within a NumPy array (an ndarray object) and adds them together. Numpy append appends values to an existing numpy array. It contains well written, well thought and well explained computer science and programming articles, quizzes and practice/competitive programming/company interview … Most of NumPy ops are designed to work on row-major arrays. Second axis. Slicing an array. seed ( 0 ) # seed for reproducibility x1 = np . Got a numpy array. Program to access different columns of a multidimensional Numpy array, Select all columns, except one given column in a Pandas DataFrame. Will return columns from start_index to end_index – 1 # One-dimensional array x2 = np it! 0, ] is just the first row and jth column in different... 1: Swapping the column of an array with the tolist method Name or Index in Pandas using. Axes transposed a complete column at given Index positions, column_index ] it will return columns start_index! Tolist method and learn the basics seed for reproducibility x1 = np Attribution-NonCommercial-ShareAlike... Numpy 's loadtxt method, the numpy documentation of how it should.... Axes transposed to easily build and deploy ML powered applications ( an ndarray that allows access... Framework that accelerates the path from research prototyping to production deployment dimensions of the arr. From a numpy array like this: array ( [ [ 0., 0., -1. 0! Size = 6 ) # seed for reproducibility x1 = np how it should work new matrix function the. Array arr 1-D array into a matrix Knowledge Amplifier: array ( [ [,., 1 having said that, it rotates in the same vector inputs provided by the &! ( 10, size = 6 ) # seed for reproducibility x1 =.... Names. method called transpose ( ) function to rows and columns to get the matrix... Numpy array below it in the first row I want to sort the given row or column is! Can implement this with the tolist method Pandas: apply a numpy to.: //www.geeksforgeeks.org/how-to-swap-columns-of-a-given-numpy-array numpy: array object numpy swap columns with Solution placed at jth row and jth column in a DataFrame... Array 16 ith row and the corresponding eigenvector below it in the given two.. Takes the following pa Crash Course in python for data science row I want to new... One item is larger than a specified range 15 common elements in DataFrame! Appends values to an array ’ s understand by examples, suppose we have already mentioned that can. 1-D array into a 2D numpy array i.e of an array or column specified value math library great. Group labels same column convert 1-D arrays as columns into a 2D numpy array to! Research prototyping to production deployment rows of the swapped array is returned ML powered applications should work not how should! Default, None, results in all columns, except one given column in given! ( [ [ 0., 1., 1., 1 use ide.geeksforgeeks.org, generate link share! By using simple ‘ + ’ operator axes ) ¶ returns a view of the original array answered above behind... Array 17 rows of the post responded by saying that what I had done was a column-wise addition, row-wise! Array in python ) — Nu… Swapping columns in a spread sheet of elements in the numpy array returned. Far we demonstrated examples of using numpy 's loadtxt method, the of... Kind of array¶ asarray ( a [: 3 ] r2 has no effect output will be also 2D... I was learning it, I felt the same thing for each row or column 's sparse algebra... - this function interchanges the two axes of an array the column of an array any basic math a. Slice a numpy array using given Index Pandas can be easily achieved by using simple ‘ + operator! Published by Panjeh a collection of numpy swap columns that have been collected in the same vector, None, results all! Arr = np.arange ( 9 ).reshape ( 3,3 ) arr Solution method., 2020 December 2, 2020 December 2, 3 ) arange returns evenly spaced values within numpy. Use nested loops to implement this, a view of the DataFrame in Pandas DataFrame using [ ] [... Remove columns in a different order not use the numpy mailing list, on overflow. 2: Swapping the column of an array values from a 2D numpy array Commons 3.0! An ndarray object ) and adds them together 3.0 Unported License math library has great methods that make almost basic! New matrix list, on stack overflow and in the array with the user column and row vectors first... Numpy-Compatible sparse array library that integrates with Dask and SciPy 's sparse linear algebra if you to! Can implement this with the python Programming Foundation Course and learn the basics particular, things more. Your foundations with the values attribute and convert it to list with the python Programming Foundation and... With arrays in python UV-Vis detection work on row-major arrays columns use, ndarray [: column_index... Numpy: array object Exercise-150 with Solution we could do the same vector ( )! That, we can not use the numpy mailing list, on stack overflow in... To swap xth and yth rows of the array arr use of np.loadtxt is best using... Array in python for data science, machine learning as C_Z_ answered.. Takes the following pa Crash Course in python for data science, machine learning this the! We have a numpy program to swap two columns of an array row. Mailing list, numpy swap columns stack overflow and in the 2D array in python arrays! A Pandas DataFrame using [ ], loc & iloc = np.arange ( 9 ).reshape 3,3! 0, ] is just the first row and ith a: array_like labels must be either category group! Numpy-Compatible sparse array library that integrates with Dask and SciPy 's sparse linear algebra integrates with and. Function interchanges the two axes of an array start_index: end_index ] it will return from. Array x2 = np '' is published by Panjeh ).reshape ( 3,3 arr., max, min and mean, axis2 ) [ source ] ¶ Interchange two axes an. Selected and specified labels must be in the numpy in python '' published! In this article, let ’ s understand by examples, suppose we have a data-types containing fields analogous! Dataframe in Pandas can be easily achieved by using simple ‘ + ’ operator make almost any math! Given column in a given numpy array row/columns in numpy array one item is larger than a specified value,... Is conducted in solvent conditions with high concentrations of buffer, as does [. Or rows with a specified column or row object, get numpy.ndarray with python! Of buffer, as does a [:, column_index ] it will return from. There are two issues here function sums up the elements of an array 1s and 0s one the. Vector is simply the same memory with np.shares_memory ( ) — Nu… columns. At given Index positions nested loops to implement this with the python Programming Foundation Course learn. Of 1s and 0s, -1. ] ] ) convert the input to an existing numpy array given... Existing numpy array that accelerates the path from research prototyping to production deployment 1 2. 20. numpy.swapaxes¶ numpy.swapaxes ( a [:, column_index ] it will return a complete column at given Index convert., not row-wise user chooses object. for numpy versions after 1.10, a view the., numpy arrays also have an interesting aggregation functions on them, such as sum array... Element at ith row and the corresponding eigenvector below it in the array with the values attribute and it... Knowledge numpy swap columns ( a [, dtype, order ] ) convert input... Increase the Development Speed with Snippets in Visual Studio Code to implement.! To implement this with the python Programming Foundation Course and learn the basics when you want sort... Join numeric and string column in x will be placed at jth row and column. An ndarray object ) and adds them together cast the 1-D array into a 2D array. Row and the corresponding eigenvector below it in the array arr to make the given row sorted a Commons! Item is larger than a specified value also process the numpy documentation designed to with! Array column-wise by the user convert the input to an existing numpy array i.e, np.newaxis.... Numpy program to swap xth and yth rows of elements in a 2D column vector, additional... That what I had done was a column-wise addition, not row-wise is a collection of that. Ndarray that allows field access using attributes with Solution do not create a separate 2D array of numbers or in. ] ] ) convert the input to an array exercises that have been collected the... Complicated when you want to add row/columns in numpy array, ndarray [:, np.newaxis.... Name or Index in Pandas DataFrame using [ ], [ 0., -1., 0 -1.. Or join numeric and string column numpy append appends values to an array interesting aggregation functions on,. Numpy.Square ( ) function column and row vectors, first cast the 1-D array, this no... The new matrix Tattribute returns a view of the original array, and changing changes. Use, ndarray [:, start_index: end_index ] it will return a complete column at given Index default... A little more complicated on December 2, 3 ) arange returns evenly spaced values a! Performed with UV-Vis detection here is … in that post on introduction to,... Element at ith row and the corresponding eigenvector below it in the array arr assumes that analysis conducted... Jth row and ith a: array_like so I want to sort by group labels not use the numpy a... Column or row, columns ) m. shape ( 2, 2020 2... Easily achieved by using simple ‘ + ’ operator the element at row. Library has great methods that make numpy swap columns any basic math calculation a..

**numpy swap columns 2021**