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How to plot a complex number in python using matplotlib ?

Article
Daidalos April 03, 2020

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Abstract: An example of how to plot a complex number in python using matplotlib: [TOC] ### Plot a complex number Let's consider the following complex number z1 = 4 + 2i [image:plot-complex-number-geometric-representation-01 size:50 caption:How to plot a complex number in python using matplotlib ?] Example of how to create a python function to plot a geometric representation of a complex number: import matplotlib.pyplot as plt import numpy as np import math z1 = 4.0 + 2.*1 ...

How to create a list of items from a string in a Django template ?

Article
Daidalos April 03, 2020

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Abstract: Example of how to split a string in a Django template [TOC] ### Introduction Let's consider the following example: with a table in models.py file with a row called tags (which is a string: models.TextField() ): class Note(models.Model): ... = ... ... = ... ... = ... tags = models.TextField() and tags is used to store labels separated by a semicolon ; (i.e. for example: New_York; Travel; Photo). The goal is to split the string tags i ...

How to create a simple maintenance page for a Django website (with Nginx, Gunicorn) on Ubuntu (digital ocean) ?

Article
Daidalos April 03, 2020

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Abstract: Simple example of how to create a python script to redirect on a maintenance page [TOC] Replace site_name by the website domain name ### Create a simple html page Go under the directory: cd /var/www/ Create the folder site_name_maintenance_page mkdir site_name_maintenance_page and then: mkdir html the path should be: /var/www/site_name_maintenance_page/html/ And create the file index.html nano index.html with the following lines <html> <head> ...

how_to_colocate_a_MODIS_granule_with_CALIOP_and_CloudSat_using_python.ipynb

Jupyter notebook
Ben April 02, 2020

How to use a specific python conda environment in a Jupyter notebook ?

Article
Daidalos March 31, 2020

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Abstract: Example of how to use a given python conda environment in a Jupyter notebook. [TOC] ### Create a conda environment To install conda go to [Anaconda Individual Edition](https://www.anaconda.com/distribution/) . Since conda is installed in your system to create an environment (called for example hereafter worklab) use the following command: conda create --name worklab and then enter source activate worklab to activate the environment called worklab. Note: to get a ...

How to iterate over rows of a pandas data frame in python ?

Article
Daidalos January 14, 2020

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Abstract: To iterate over rows of a pandas data frame in python, a solution is to use [iterrows()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.iterrows.html), [items()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.items.html#pandas.DataFrame.items) or [itertuples()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.itertuples.html#pandas.DataFrame.itertuples): [TOC] Let's consider the following pandas data fram ...

How to sum a given row of a data array in python with numpy ?

Article
Daidalos December 05, 2019

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Abstract: Example of how to sum a given row of a data array in python with numpy: [TOC] ### Sum a row of data Lets consider the following array: >>> import numpy as np >>> data = np.arange(80).reshape((8, 10)) >>> data array([[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [10, 11, 12, 13, 14, 15, 16, 17, 18, 19], [20, 21, 22, 23, 24, 25, 26, 27, 28, 29], [30, 31, 32, 33, 34, 35, 36, 37, 38, 39], [40, 41, 42, 43, 44, 45, 46, 47, 48, 49], [50, 51, 52, 53, 54, 55, ...

How to sum a given column of a data array in python with numpy ?

Article
Daidalos December 05, 2019

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Abstract: Example of how to sum a column of data in python with numpy: [TOC] ### Sum a given column of data Let's consider the following matrix >>> import numpy as np >>> data = np.arange(80).reshape((8, 10)) >>> data array([[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [10, 11, 12, 13, 14, 15, 16, 17, 18, 19], [20, 21, 22, 23, 24, 25, 26, 27, 28, 29], [30, 31, 32, 33, 34, 35, 36, 37, 38, 39], [40, 41, 42, 43, 44, 45, 46, 47, 48, 49], [50, 51, 52, 53, 54, 55, ...

How to randomly select elements of an array with numpy in python ?

Article
Daidalos November 26, 2019

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Abstract: Examples of how to randomly select elements of an array with numpy in python: [TOC] ### Randomly select elements of a 1D array using choice() Lets create a simple 1D array with 10 elements: >>> import numpy as np >>> data = np.arange(10) >>> data array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) \begin{equation} A = \left( \begin{array}{ccc} 0 & 1& 2& 3& 4& 5& 6& 7& 8& 9 \end{array}\right) \end{equation} To select randomly n elements, a solution is to use [choice()](https://do ...

How to randomly select rows of an array in python with numpy ?

Article
Daidalos November 26, 2019

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Abstract: Examples of how to randomly select rows of an array in python with numpy: [TOC] ### Create an array with numpy Let create the following array: >>> import numpy as np >>> data = np.arange(80).reshape((8, 10)) >>> data array([[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [10, 11, 12, 13, 14, 15, 16, 17, 18, 19], [20, 21, 22, 23, 24, 25, 26, 27, 28, 29], [30, 31, 32, 33, 34, 35, 36, 37, 38, 39], [40, 41, 42, 43, 44, 45, 46, 47, 48, 49], [50, 51, ...

How to upload from ICARE a MODIS L2 granule using ftp and python 3 ?

Article
Ben November 25, 2019

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Abstract: Example of how to upload with ftp a MODIS granule from ICARE server to my local machine in python 3. [TOC] Import python modules from ftplib import FTP from datetime import date import numpy as np import calendar Granule date & time year = 2008 month = 1 day = 8 hour = 14 minutes = 20 Retrieve count of days: d = date(year, month, day) - date(year, 1, 1) File name file = 'MYD06_L2.A{:04d}{:03d}.{:02d}{:02d}'.format(year,d.days+1,hour,minutes) P ...

How to change the color background of a matplotlib figure ?

Article
Daidalos November 20, 2019

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Abstract: Examples of how to change the color background of a matplotlib figure: [TOC] ### Using subplot and the option axisbg from pylab import * subplot(111, axisbg='#ababab') t = arange(0.0, 2.0, 0.01) s = sin(2*pi*t) plot(t, s) xlabel('x') ylabel('y') title('How to change background color in matplotlib ?') savefig('exemple_01.png') show() [image:376 size:50 caption:How to change the color background of a matplotlib figure ?] source: [How to set opacity of backgroun ...

Elementary operations on lists in python

Article
Daidalos November 20, 2019

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Abstract: Examples of elementary operations on lists in python [TOC] ### Create a list Create an empty list >>> l = [] >>> type(myfirstlist) <type 'list'> Create a list with 3 elements >>> l = ['a','b','c'] Note: in a list the elements can have different typrs >>> l = ['hello',1,2] ### Get the number of elements in a list To get the number of elements in a list a solution is to use len() >>> l = ['Pierre', 'Paul', 'Mathieu'] >>> len(l) 3 ...

How to sum / add two or several matrices together in python ?

Article
Daidalos November 20, 2019

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Abstract: Examples of how to sum / add two or several matrices together in python using numpy: [TOC] ### Add two matrices of same size Let sum two matrices of same size. Let's consider the matrix A: >>> import numpy as np >>> A = np.array(([3,1],[6,4])) >>> A array([[3, 1], [6, 4]]) \begin{equation} A = \left( \begin{array}{ccc} 3 & 1 \\\\ 6 & 4 \end{array}\right) \end{equation} and matrix B: >>> B = np.array(([1,8],[4,2])) >>> B array([[1, 8], [4, 2]] ...

How to get a complex number in polar coordinates in python ?

Article
Daidalos November 16, 2019

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Abstract: Examples of how to get a complex number in polar coordinates in python: [TOC] ### Using the python module cmath To get a complex number in polar coordinate a solution is to use the python module [cmath](https://docs.python.org/2/library/cmath.html): >>> import cmath Let's consider the following complex number: >>> z = 2 + 3j to get the polar coordinates: >>> r,theta = cmath.polar(z) >>> r 3.605551275463989 >>> theta 0.982793723247329 Note: to return the c ...

How to create a matrix of complex numbers in python using numpy ?

Article
Daidalos November 15, 2019

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Abstract: Examples of how to create a matrix of complex numbers in python using numpy: [TOC] ### Create a matrix of random numbers >>> Z = np.array([[1+2j,1+3j],[5+6j,3+8j]]) >>> Z array([[ 1.+2.j, 1.+3.j], [ 5.+6.j, 3.+8.j]]) ### Create a matrix of random numbers with 0+0j >>> import numpy as np >>> Z = np.zeros(10, dtype=complex) >>> Z array([ 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0. ...

How to get the conjugate of a complex number in python ?

Article
Daidalos November 15, 2019

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Abstract: Examples of how to get the conjugate of a complex number z in python: [TOC] ### Get the conjugate of a complex number A solution is to use the python function [conjugate()](http://stackoverflow.com/questions/8370637/complex-numbers-usage-in-python), example >>> z = complex(2,5) >>> z.conjugate() (2-5j) >>> ### Matrix of complex numbers Another example using a matrix of complex numbers import numpy as np >>> Z = np.random.random(10) + np.random. ...

How to extract the real and imaginary parts of a complex number in python ?

Article
Daidalos November 15, 2019

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Abstract: To extract the the real and imaginary parts of a complex number z=a+ib in python, a solution is to use z.real and z.imag: [TOC] ### Extract the real and imaginary parts of a complex number >>> z = complex(2,5) >>> z (2+5j) >>> z.real 2.0 >>> z.imag 5.0 ### Matrix of complex number It also works with matrix of complex numbers: >>> import numpy as np >>> Z = np.array([[1+2j,1+3j],[5+6j,3+8j]]) >>> Z array([[ 1.+2.j, 1.+3.j], [ 5.+6. ...

How to get the modulus of complex number in python ?

Article
Daidalos November 15, 2019

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Abstract: Examples of how to get the modulus of complex number in python: [TOC] ### Definition The modulus of complex number $z=a+ib$ is: \begin{equation} |z| = |a+ib| = \sqrt{a^2+b^2} \end{equation} with $a$ and $b$ are the real and imaginary parts. ### Create a function to calculate the modulus of complex number To calculate the modulus of complex number a solution is to define a simple python function: >>> import math >>> def complexe_modulo(z): ... a = z.r ...

How to copy a dataframe with pandas in python ?

Article
Daidalos November 14, 2019

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Abstract: Example of how to copy a data frame with pandas in python: [TOC] ### Create a dataframe To start let's create a simple dataframe: >>> import pandas as pd >>> import numpy as np >>> data = np.random.randint(100, size=(10,5)) >>> df = pd.DataFrame(data=data,columns=['a','b','c','d','e']) >>> df a b c d e 0 42 94 3 22 28 1 0 85 93 43 18 2 70 10 98 19 26 3 54 72 89 51 61 4 13 44 94 28 34 5 79 4 89 33 81 6 69 37 84 89 ...

How to prepend an n-by-1 column of ones to a matrix in python using numpy ? (machine learning)

Article
Daidalos November 14, 2019

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Abstract: Examples of how to prepend an n-by-1 column of ones to a matrix of training input data: [TOC] ### Prepend an n-by-1 column of ones to a training dataset Let's consider the following matrix X of training data X (with n=6 observations and d=3 features): \begin{equation} X = \left( \begin{array}{ccc} x_{11} & x_{12} & x_{13} \\\\ x_{21} & x_{22} & x_{23} \\\\ x_{31} & x_{32} & x_{33} \\\\ x_{41} & x_{42} & x_{43} \\\\ x_{51} & x_{52} & x_{53} \\\\ x_{61} & x_{62} & x_{63} \end ...

How to count the occurrence of an element in a pandas data frame column ?

Article
Daidalos November 08, 2019

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Abstract: Examples of how to count the occurrence of an element in a pandas data frame column: [TOC] ### Using value_counts() Lets take for example the file ['default of credit card clients Data Set"](https://archive.ics.uci.edu/ml/datasets/default+of+credit+card+clients#) that can be downloaded [here](https://archive.ics.uci.edu/ml/machine-learning-databases/00350/) >>> import pandas as pd >>> df = pd.read_excel('default of credit card clients.xls', header=1) To get the count of d ...

How to get the shape of a DataFrame in python with pandas ?

Article
Daidalos November 08, 2019

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Abstract: Examples of how to get the shape of a DataFrame in python with panda: [TOC] ### Get DataFrame shape Let's consider the following file train.csv (that can be downloaded on kaggle): >>> import pandas as pd >>> df = pd.read_csv('train.csv') To get the shape a solution is to use the function [shape()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.shape.html): >>> print(df.shape) (1460, 81) ### Number of columns Get the number of columns ...

How to read a simple text file in python ?

Article
Daidalos November 08, 2019

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Abstract: Example of how to read a simple text file in python: [TOC] ### Read a text file Let's consider the following file [iso_8859-1.txt](https://www.w3.org/TR/PNG/iso_8859-1.txt). To read and close the file do: f = open('iso_8859-1.txt', 'r') f.closed ### Get all the file content To get all the file content a solution is to use f.read(): f = open('iso_8859-1.txt', 'r') data = f.read() f.close and print the content using print(data) returns here: Th ...

How to add some text on a matplotlib figure in python ?

Article
Daidalos November 07, 2019

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Abstract: Examples of how to add some text on a matplotlib figure in python: [TOC] ### Add text using pyplot.text() To add some text on a matplotlib figure, a solution is to use the function [matplotlib.pyplot.text()](http://matplotlib.org/api/pyplot_api.html?highlight=figtext) that needs the position of the text (x,y) and the text itself. An example with the text 'Hello World !' at the coordinates (1,35): #!/usr/bin/env python import numpy as np import matplotlib.pyplot as plt x ...

How to rename a column name of a DataFrame in pandas ?

Article
Daidalos November 07, 2019

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Abstract: Examples of how to rename a column name of a DataFrame in pandas: [TOC] ### Rename a column name using rename() Let's consider the following dataframe >>> import numpy as np >>> import pandas as pd >>> import numpy as np >>> data = np.random.randint(100, size=(5,5)) >>> df = pd.DataFrame(data=data,columns=['c1','c2','c3','c4','c5']) >>> df c1 c2 c3 c4 c5 0 33 93 44 10 38 1 77 27 78 15 84 2 33 50 42 30 63 3 35 54 39 8 21 4 77 11 3 ...

How to remove one or multiple rows in a pandas DataFrame in python ?

Article
Daidalos November 01, 2019

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Abstract: Examples of how to remove one or multiple rows in a pandas DataFrame in python [TOC] ### Remove one row Lets create a simple dataframe with pandas >>> data = np.random.randint(100, size=(10,10)) >>> df = pd.DataFrame(data=data) >>> df 0 1 2 3 4 5 6 7 8 9 0 13 44 3 55 13 98 44 87 20 52 1 72 72 96 18 68 84 81 41 8 75 2 53 71 97 27 21 44 61 9 59 87 3 40 94 49 7 56 93 17 62 71 14 4 4 20 56 45 89 78 9 ...

How to remove one or multiple columns in a pandas DataFrame in python ?

Article
Daidalos November 01, 2019

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Abstract: Examples of how to remove one or multiple columns in a pandas DataFrame in python: [TOC] ### Remove one column Lets create a simple dataframe >>> import pandas as pd >>> import numpy as np >>> data = np.random.randint(100, size=(10,10)) >>> data array([[55, 38, 97, 91, 22, 12, 87, 55, 38, 91], [44, 39, 64, 45, 33, 26, 28, 9, 86, 40], [10, 98, 55, 3, 99, 41, 25, 8, 36, 47], [84, 82, 55, 73, 29, 28, 85, 99, 7, 92], [84, 38, 45, 75, 9, 45, 89, 19, 6 ...

How to select one or multiple rows in a pandas DataFrame in python ?

Article
Daidalos November 01, 2019

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Abstract: Examples of how to select one or multiple rows in a pandas DataFrame in python: [TOC] ### Create a DataFrame Lets consider the following dataset train.csv (that can be downloaded on [kaggle](https://www.kaggle.com/c/house-prices-advanced-regression-techniques/data)). To read the file a solution is to use [read_csv()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_csv.html): >>> import pandas as pd >>> df = pd.read_csv('train.csv') >>> df.shape (1460, 8 ...

How to replace some elements of a matrix using numpy in python ?

Article
Daidalos October 31, 2019

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Abstract: Examples of how to replace some elements of a matrix using numpy in python: [TOC] ### Replace some elements of a 1D matrix Let's try to replace the elements of a matrix called M strictly lower than 5 by the value -1: >>> import numpy as np >>> M = np.arange(10) >>> M array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) >>> M[M > 5 ] = -1 >>> M array([ 0, 1, 2, 3, 4, 5, -1, -1, -1, -1]) ### Replace some elements of a 2D matrix Another exam ...

How to select one or multiple columns in a pandas DataFrame in python ?

Article
Daidalos October 29, 2019

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Abstract: Example of how to extract one or several columns of data in a pandas dataframe [TOC] ### Create a dataframe with pandas Let's consider the csv file train.csv (that can be downloaded on [kaggle](https://www.kaggle.com/c/house-prices-advanced-regression-techniques/data)). To read the file a solution is to use [read_csv()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_csv.html): >>> import pandas as pd >>> df = pd.read_csv('train.csv') >>> df.shape (1460 ...

How to extract one or several columns of data in a pandas dataframe ?

Article
Daidalos October 29, 2019

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Abstract: Exemple de comment sélectionner une ou des colonnes de données dans une DataFrame avec pandas ? [TOC] ### Créer une DataFrame avec Pandas Soit par exemple le fichier csv suivant train.csv (que l'on peut télécharger sur [kaggle](https://www.kaggle.com/c/house-prices-advanced-regression-techniques/data)). Pour lire le fichier il existe la fonction pandas [read_csv()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_csv.html): >>> import pandas as pd >>> df = ...

How to filter missing data (NAN or NULL values) in a pandas DataFrame ?

Article
Daidalos October 28, 2019

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Abstract: Examples of how to work with missing data (NAN or NULL values) in a pandas DataFrame: [TOC] ### Create a DataFrame with Pandas Let's consider the csv file train.csv (that can be downloaded on [kaggle](https://www.kaggle.com/c/house-prices-advanced-regression-techniques/data)). To read the file a solution is to use [read_csv()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_csv.html): >>> import pandas as pd >>> data = pd.read_csv('train.csv') Get DataFr ...

How to add metadata to a data frame with pandas in python ?

Article
Daidalos October 22, 2019

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Abstract: Example of how to add metadata to a data frame with pandas in python: [TOC] ### Create a data frame with pandas Example of how to create a simple data frame with pandas import pandas as pd import numpy as np data = np.arange(1,13) data = data.reshape(3,4) columns = ['Home','Car','Sport','Food'] index = ['Alice','Bob','Emma'] df = pd.DataFrame(data=data,index=index,columns=columns) ### Add metadata A solution to add metadata: df.scale = 0.1 df.offset = 1 ...

How to save a large dataset in a hdf5 file using python ? (Quick Guide)

Article
Daidalos October 22, 2019

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Abstract: Examples of how to store a large dataset in a hdf5 file using python: [TOC] ### Create arrays of data Let's consider the following matrices of integers (dtype='i'): >>> import numpy as np >>> A = np.random.randint(100, size=(4,4)) >>> A array([[ 1, 99, 79, 46], [69, 4, 29, 60], [56, 94, 16, 16], [52, 13, 37, 86]]) matrix B of dimensions (5,3,3) >>> B = np.random.randint(100, size=(5,3,3)) >>> B array([[[60, 89, 24], [ 4, 98, 48], [19, 39, ...

How to get the names (titles or labels) of a pandas data frame in python ?

Article
Daidalos October 21, 2019

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Abstract: Examples of how to get the names (titles or labels) of a pandas data frame in python [TOC] ### Get the row names of a pandas data frame Let's consider a data frame called df. to get the row names a solution is to do: >>> df.index ### Get the row names of a pandas data frame (Exemple 1) Let's create a simple data frame: >>> import pandas as pd >>> import numpy as np >>> data = np.arange(1,13) >>> data = data.reshape(3,4) >>> data array([[ 1, 2, 3, 4], ...

How to read a csv file using pandas in python ?

Article
Daidalos October 20, 2019

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Abstract: Example of how to read a csv file using pandas in python: [TOC] ### Read a csv file Let's consider the csv file train.csv (that can be downloaded on [kaggle](https://www.kaggle.com/c/house-prices-advanced-regression-techniques/data)). To read the csv file a solution is to use the pandas function [read_csv()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_csv.html): >>> import pandas as pd >>> data = pd.read_csv('train.csv') Get array dimensions: >>> ...

How to extract columns names of a pandas dataframe in python ?

Article
Daidalos October 20, 2019

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Abstract: With pandas to get the names of a dataframe, there is the attribute columns ([ref](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.columns.html)): >>> DataFrame.columns Examples of applications: [TOC] ### Read a cvs data file and create a dataframe with pandas Let's consider the cvs data file train.csv (that can be downloaded on [kaggle](https://www.kaggle.com/c/house-prices-advanced-regression-techniques/data)) >>> import pandas as pd >>> dat ...

How to get the number of dimensions of a matrix using numpy in python ?

Article
Daidalos October 17, 2019

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Abstract: Exemple de comment déterminer le nombre de dimensions d'une matrice en python: [TOC] ### Get the number of dimensions of a matrix Let's consider the following matrix: >>> import numpy as np >>> A = np.array([[3,9,4],[5,8,1],[9,2,5]]) >>> A array([[3, 9, 4], [5, 8, 1], [9, 2, 5]]) To get the shape of the matrix, a solution is to first use [shape](https://docs.scipy.org/doc/numpy/reference/generated/numpy.ndarray.shape.html): >>> A.shape (3, 3) and ...

How to create an identity matrix using numpy in python ?

Article
Daidalos October 17, 2019

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Abstract: Examples of how to create an identity matrix using numpy in python ? [TOC] ### Using the numpy function identity Let's create the following identity matrix \begin{equation} I = \left( \begin{array}{ccc} 1 & 0 & 0 \\\\ 0 & 1 & 0 \\\\ 0 & 0 & 1 \end{array}\right) \end{equation} using numpy function identity: >>> import numpy as np >>> I = np.identity(3) >>> I array([[ 1., 0., 0.], [ 0., 1., 0.], [ 0., 0., 1.]]) Another example: \begin{ ...

How to create a data frame in python using pandas ?

Article
Daidalos October 15, 2019

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Abstract: Examples of how to create a data frame using the python module pandas [TOC] ### Create a data frame using an array Import pandas and numpy: >>> import pandas as pd >>> import numpy as np Let's consider the following matrix \begin{equation} data = \left( \begin{array}{ccc} 1 & 2 & 3 & 4 \\\\ 5 & 6 & 7 & 8 \\\\ 9 & 10 & 11 & 12 \end{array}\right) \end{equation} >>> data = np.arange(1,13) >>> data = data.reshape(3,4) >>> data array([[ 1, 2, 3, 4], [ 5 ...

How to create and initialize a matrix in python using numpy ?

Article
Daidalos October 11, 2019

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Abstract: To create and initialize a matrix in python, there are several solutions, some commons examples using the python module numpy: [TOC] ### Create a simple matrix Create a 1D matrix of 9 elements: \begin{equation} A = \left( \begin{array}{ccc} 1&7& 3& 7& 3& 6& 4& 9& 5 \end{array}\right) \end{equation} >>> import numpy as np >>> A = np.array([1,7,3,7,3,6,4,9,5]) >>> A array([1, 7, 3, 7, 3, 6, 4, 9, 5]) Notice: the shape of the matrix A is here (9,) and not (9,1) >>> ...

The MODIS Cloud Optical and Microphysical Products: Collection 6

PDF File
Ben October 10, 2019

Abstract: Cloud thermodynamic phase (ice, liquid, undetermined) classification is an important first step for cloud retrievals from passive sensors such as MODIS (Moderate Resolution Imaging Spectroradiometer). Because ice and liquid phase clouds have very different scattering and absorbing properties, an incorrect cloud phase decision can lead to substantial errors in the cloud optical and microphysical property products such as cloud optical thickness or effective particle radius. Furthermore, it is wel ...

How to create a list of uniformly spaced numbers using a logarithmic scale with python ?

Article
Daidalos October 10, 2019

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Abstract: Example of how to create a list of uniformly spaced numbers using a logarithmic scale with python: [TOC] ### Using the numpy function logspace Let's create a list of 100 uniformly spaced numbers (between $10^{0.1}$ et $10^{3}$) using a logarithmic scale >>> import numpy as np >>> l = np.logspace(0.1, 3, 100, endpoint=True) >>> l array([ 1.25892541, 1.34676844, 1.44074081, 1.54127022, 1.64881419, 1.76386217, 1.88693776, 2.0 ...

How to find the indexes of the minimum or maximum value(s) in a matrix using python ?

Article
Daidalos October 08, 2019

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Abstract: Examples of how to find the indexes of the minimum or maximum value(s) in a matrix using python and the numpy function called [where](https://docs.scipy.org/doc/numpy/reference/generated/numpy.where.html): [TOC] Let's consider the following 2D matrix: >>> import numpy as np >>> A = np.random.randint(100, size=(4, 4)) >>> A array([[73, 37, 6, 21], [16, 53, 77, 44], [98, 95, 3, 29], [77, 67, 87, 86]]) ### Find min and max values First, to find the minimum ...

How to restore Aqua MODIS Band 6 missing pixels ?

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Ben October 08, 2019

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Abstract: Ongoing research ... Goal: To develop an algorithm (in python) based on Gaussian processes to restore the Aqua MODIS Band 6 missing pixels: [images:modis-band6-missing-data-restoration-01;modis-band6-missing-data-restoration-11 dim:1*2 size:80 caption:Aqua MODIS Band 6 missing pixels restoration using Gaussian processes] [TOC] ### Get and plot the data #!/usr/bin/env python from pyhdf.SD import SD, SDC from pylab import figure, cm import numpy as np import matplotlib ...

How to delete rows with values ​​below and above a minimum and maximum value in a pandas data frame ?

Article
Daidalos October 05, 2019

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Abstract: A solution to delete rows with values ​​below and above a minimum and maximum value in a pandas data frame is to use the function [between()](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.between.html). Let's consider the following data frame >>> import pandas as pd >>> data = {'Label':['a','b','c','d','e','f','g','h','i','j'],'Value 1':[0,9,3,7,2,6,5,9,6,3], 'Value 2':[56,34,99,11,78,89,34,94,65,36]} >>> df = pd.DataFrame(data) >>> df Label Value 1 V ...

How to convert a pdf document pages to images using python ?

Article
Daidalos October 01, 2019

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Abstract: Examples of how to convert a pdf document pages to images using python [TOC] ## 1. Using the python module pdf2image The python module pdf2image is available on [github](https://github.com/Belval/pdf2image). To install it a solution is to use pip: pip install pdf2image Note: the module needs poppler to run. If you use anaconda python distrubtion, it can be installed for example using the following command: conda install -c conda-forge poppler Then the module can now ...

How to create a matrix of random integers in python ?

Article
Daidalos October 01, 2019

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Abstract: To create a matrix of random integers in python, a solution is to use the numpy function [randint](https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.random.randint.html), examples: [TOC] ### 1D matrix with random integers between 0 and 9: Example of 1D matrix with 20 random integers between 0 and 9: >>> import numpy as np >>> A = np.random.randint(10, size=(20)) >>> A array([1, 8, 4, 3, 5, 7, 1, 2, 9, 6, 7, 6, 3, 1, 4, 6, 4, 9, 9, 6]) returns for example: ...

How to use Gaussian processes in machine learning to do a regression or classification using python 3 ?

Article
Daidalos August 08, 2019

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Abstract: Examples of how to use Gaussian processes in machine learning to do a regression or classification using python 3: [TOC] ### A 1D example: from numpy.linalg import inv import matplotlib.pyplot as plt import numpy as np X = np.array([1., 3., 5., 6., 7., 8.]) Y = X * np.sin(X) X = X[:,np.newaxis] sigma_n = 1.5 plt.grid(True,linestyle='--') plt.errorbar(X, Y, yerr=sigma_n, fmt='o') plt.title('Gaussian Processes for regression (1D Case) Training Data', f ...

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