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12 #+LaTeX_HEADER: \usepackage[english]{babel} \usepackage{ae,aecompl} |
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13 #+LaTeX_HEADER: \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet} |
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14 |
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15 #+LaTeX_HEADER: \usepackage{listings} |
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16 |
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17 #+LaTeX_HEADER:\lstset{language=Python, basicstyle=\ttfamily\bfseries, |
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18 #+LaTeX_HEADER: commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen}, |
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19 #+LaTeX_HEADER: showstringspaces=false, keywordstyle=\color{blue}\bfseries} |
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20 |
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21 #+TITLE: Accessing parts of arrays |
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22 #+AUTHOR: FOSSEE |
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23 #+EMAIL: |
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24 #+DATE: |
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25 |
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26 #+DESCRIPTION: |
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27 #+KEYWORDS: |
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28 #+LANGUAGE: en |
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29 #+OPTIONS: H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t |
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30 #+OPTIONS: TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc |
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31 |
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32 * Outline |
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33 - Manipulating one and multi dimensional arrays |
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34 - Access and change individual elements |
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35 - Access and change rows and columns |
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36 - Slicing and striding on arrays to access chunks |
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37 - Read images into arrays and manipulations |
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38 * Sample Arrays |
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39 #+begin_src python |
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40 In []: A = array([12, 23, 34, 45, 56]) |
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41 |
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42 In []: C = array([[11, 12, 13, 14, 15], |
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43 [21, 22, 23, 24, 25], |
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44 [31, 32, 33, 34, 35], |
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45 [41, 42, 43, 44, 45], |
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46 [51, 52, 53, 54, 55]]) |
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47 |
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48 #+end_src |
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49 * Question 1 |
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50 Change the last column of ~C~ to zeroes. |
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51 * Solution 1 |
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52 #+begin_src python |
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53 In []: C[:, -1] = 0 |
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54 #+end_src |
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55 * Question 2 |
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56 Change ~A~ to ~[11, 12, 13, 14, 15]~. |
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57 * Solution 2 |
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58 #+begin_src python |
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59 In []: A[:] = [11, 12, 13, 14, 15] |
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60 #+end_src |
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61 * squares.png |
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62 #+begin_latex |
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63 \begin{center} |
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64 \includegraphics[scale=0.6]{squares} |
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65 \end{center} |
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66 #+end_latex |
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67 * Question 3 |
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68 - obtain ~[22, 23]~ from ~C~. |
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69 - obtain ~[11, 21, 31, 41]~ from ~C~. |
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70 - obtain ~[21, 31, 41, 0]~. |
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71 * Solution 3 |
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72 #+begin_src python |
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73 In []: C[1, 1:3] |
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74 In []: C[0:4, 0] |
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75 In []: C[1:5, 0] |
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76 #+end_src |
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77 * Question 4 |
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78 Obtain ~[[23, 24], [33, -34]]~ from ~C~ |
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79 * Solution 4 |
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80 #+begin_src python |
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81 In []: C[1:3, 2:4] |
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82 #+end_src |
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83 * Question 5 |
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84 Obtain the square in the center of the image |
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85 * Solution 5 |
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86 #+begin_src python |
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87 In []: imshow(I[75:225, 75:225]) |
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88 #+end_src |
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89 * Question 6 |
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90 Obtain the following |
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91 #+begin_src python |
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92 [[12, 0], [42, 0]] |
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93 [[12, 13, 14], [0, 0, 0]] |
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94 #+end_src |
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95 |
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96 * Solution 6 |
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97 #+begin_src python |
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98 In []: C[::3, 1::3] |
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99 In []: C[::4, 1:4] |
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100 #+end_src |
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101 * Summary |
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102 You should now be able to -- |
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103 - Manipulate 1D \& Multi dimensional arrays |
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104 - Access and change individual elements |
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105 - Access and change rows and columns |
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106 - Slice and stride on arrays |
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107 - Read images into arrays and manipulate them. |
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108 * Thank you! |
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109 #+begin_latex |
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110 \begin{block}{} |
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111 \begin{center} |
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112 This spoken tutorial has been produced by the |
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113 \textcolor{blue}{FOSSEE} team, which is funded by the |
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114 \end{center} |
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115 \begin{center} |
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116 \textcolor{blue}{National Mission on Education through \\ |
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117 Information \& Communication Technology \\ |
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118 MHRD, Govt. of India}. |
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119 \end{center} |
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120 \end{block} |
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121 #+end_latex |
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122 |
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123 |