There are 3 methods to convert 2-D arrays to 1-D ones in Numpy. The following shows the key syntax. Method 1: numpy.ravel() Method 2: ndarray.flatten(order=’C’) Method 3: ndarray.reshape(-1) Example 1 (Method 1): We can use numpy.ravel() to convert 2-D arrays to 1-D ones. Below is the example. Output: 2-D array: [[ 5 2 3 4 … Read more
You might encounter the following error when trying to convert Numpy arrays to a pandas dataframe. Exception: Data must be 1-dimensional 1. Reproduce the Error Output: Exception: Data must be 1-dimensional 2. Why the Error Happens It happens because pd.DataFrame is expecting to have 1-D numpy arrays or lists, since it is how columns within … Read more
This tutorial will show how you can combine multiple arrays (e.g., 2 arrays of X and Y) into a Pandas dataframe. The following summarizes the two methods. Method 1: pd.DataFrame ({‘X’:X,’Y’:Y}) Method 2: combined_array=np.column_stack((X,Y))pd.DataFrame(combined_array, columns = [‘X’,’Y’]) Two Examples of Combining Arrays into Dataframe Example for Method 1: In the following, we create two arrays, … Read more
Np.dot() in Python Numpy generates the product of two arrays. Specifically, for np.dot(a, b), Situation 1: If both a and b are 1-D arrays, it is inner product of vectors. Situation 2: If both a and b are 2-D arrays, it is matrix multiplication. Using matmul or a @ b is preferred. Situation 3: If either a or b is 0-D (scalar), it is equivalent to multiply. Using np.multiply(a, b) or a * b is preferred. Example 1: … Read more
This tutorial provides 3 methods to create 2-D Numpy Arrays in Python. The following is the key syntax for these 3 methods. After that, 3 Python Numpy code examples are provided. Method 1: np.array[[numbers in the first row ], [numbers in the second row]] Method 2: np.zeros(shape(row number, column number)) Method 3: array_name=np.arange(length number)array_name=array_name.reshape(row number, … Read more
You can use the np.isscalar() to check whether a variable is a scalar or array. The following shows Python code examples checking it is a scalar or array. Example 1: A number Output: True Example 2: An array with one number Output: False Since it is not a scalar, we can check whether it is … Read more
You can use pd.DataFrame() function to convert an array to a column in a Pandas dataframe. The following shows examples of how to convert array from Numpy to a column in Pandas. Example 1: Single Column Step 1: Using Numpy to create an array Output: [‘City1’ ‘City1’ ‘City1’ ‘City1’ ‘City1’ ‘City2’ ‘City2’ ‘City2’ ‘City2’ ‘City2’] … Read more
The syntax of creating an empty array is as follows. Method 1: Full of zero numpy.zeros(shape=(n,m)) Method 2: Really empty Note that, empty, unlike zeros, does not set the array values to zero, and may therefore be marginally faster. However, it requires the user to manually set all the values in the array, and thus you … Read more
We can use tolist() and list() to convert an array into a list in Python. The following is the syntax. Method 1: array.tolist() Method 2: list(array) The following is to generate an array using Numpy. Array_1: [5 8 4 4] Method 1: np.tolist() list_1: [5, 8, 4, 4] Method 2: list() We can use Python … Read more
You can add a NumPy array as a new column to Pandas dataframes by using the tolist() function. The following are the syntax statement as well as examples showing how to actually do it. df[‘new_column_name’] = array_name.tolist() Step 1: Generate a sample dataframe The following is to generate a dataframe and then print it out. … Read more