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1 .. Objectives |
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2 .. ---------- |
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3 |
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4 .. At the end of this tutorial, you will be able to |
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5 |
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6 .. 1. Save plots using ``savefig()`` function. |
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7 .. #. Save plots in different formats. |
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8 |
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9 |
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10 .. Prerequisites |
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11 .. ------------- |
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12 |
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13 .. 1. should have ``ipython`` and ``pylab`` installed. |
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14 .. #. getting started with ``ipython``. |
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15 .. #. using plot command interactively. |
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16 |
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17 .. Author : Anoop Jacob Thomas <anoop@fossee.in> |
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18 Internal Reviewer : Puneeth |
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19 External Reviewer : |
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20 Language Reviewer : Bhanukiran |
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21 Checklist OK? : <10-11-2010, Anand, OK> [2010-10-05] |
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22 |
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23 .. #[Puneeth: Quickref missing.] |
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24 |
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25 ======= |
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26 Savefig |
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27 ======= |
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28 |
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29 {{{ Show the first slide }}} |
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30 |
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31 Hello and welcome to the tutorial saving plots. |
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32 |
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33 {{{ switch to next slide, outline slide }}} |
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34 |
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35 In this tutorial you will learn how to save plots using Python, saving |
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36 in different formats, and locating the file in the file system. |
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37 |
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38 .. #[Puneeth: file-system is too technical.] |
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39 |
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40 {{{ switch to next slide, a sine wave}}} |
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41 |
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42 Start your IPython interpreter with the command :: |
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43 |
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44 ipython -pylab |
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45 |
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46 As you know, it will start your IPython interpreter with the required |
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47 python modules for plotting and saving your plots. |
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48 |
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49 {{{ Open ipython }}} |
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50 |
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51 Now let us plot something, let us plot a sine wave from minus 3 pi to |
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52 3 pi. Let us start by calculating the required points for the plot. It |
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53 can be done using linspace as, :: |
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54 |
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55 x = linspace(-3*pi,3*pi,100) |
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56 |
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57 We have stored required points in x. Now let us plot the points using |
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58 the statement :: |
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59 |
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60 plot(x,sin(x)) |
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61 |
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62 {{{ Keep the plot open }}} |
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63 |
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64 Done! we have made a very basic sine plot, now let us see how to save |
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65 the plot for future use so that you can embed the plot in your |
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66 reports. |
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67 |
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68 .. #[Puneeth: All this is known stuff. You don't have to elaborate so |
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69 .. much on it. Just say, let us plot sin function from -3 pi to 3 |
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70 .. pi. Show the commands, and be done with it. ] |
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71 |
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72 {{{ switch to next slide, savefig() }}} |
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73 |
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74 {{{ Switch the focus to IPython interpreter window }}} |
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75 |
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76 For saving the plot, we will use ``savefig()`` function, and it has to be |
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77 done with the plot window open. The statement is, :: |
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78 |
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79 savefig('/home/fossee/sine.png') |
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80 |
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81 Notice that ``savefig`` function takes one argument which is the |
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82 filename. The last 3 characters after the ``.`` in the filename is the |
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83 extension or type of the file which determines the format in which you |
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84 want to save. |
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85 |
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86 .. #[Puneeth: removed mention of string] |
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87 |
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88 .. #[[Anoop: I think this treatment is better :) ]] |
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89 |
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90 {{{ Highlight the /home/fossee part using mouse movements }}} |
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91 |
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92 Also, note that we gave the full path or the absolute path to which we |
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93 want to save the file. |
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94 |
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95 {{{ Highlight the .png part using mouse movements }}} |
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96 |
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97 Here I have used an extension ``.png`` which means I want to save the |
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98 image as a PNG file. |
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99 |
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100 Now let us locate ``sine.png`` file saved. We saved the file to |
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101 ``/home/fossee`` so let us navigate to ``/home/fossee`` using the |
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102 file browser. |
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103 |
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104 {{{ Open the browser, navigate to /home/fossee and highlight the file |
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105 sine.png }}} |
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106 |
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107 Yes, the file ``sine.png`` is here and let us check it. |
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108 |
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109 {{{ Open the file sine.png and show it for two-three seconds and then |
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110 close it and return to IPython interpreter, make sure the plot window |
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111 is still open, also don't close the file browser window }}} |
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112 |
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113 {{{ switch to next slide, More on savefig() }}} |
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114 |
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115 So in-order to save a plot, we use ``savefig`` function. ``savefig`` |
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116 can save the plot in many formats, such as pdf - portable document |
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117 format, ps - post script, eps - encapsulated post script, svg - |
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118 scalable vector graphics, png - portable network graphics which |
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119 support transparency etc. |
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120 |
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121 .. #[[slide must give the extensions for the files - Anoop]] |
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122 |
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123 {{{ switch to next slide, exercise 1 }}} |
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124 |
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125 Let us now try to save the plot in eps format. ``eps`` stands for |
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126 encapsulated post script, and it can be embedded in your latex |
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127 documents. Pause here and try to figure it out yourself. |
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128 |
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129 {{{ Switch focus to the already open plot window }}} |
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130 |
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131 We still have the sine plot with us, and now let us save the plot as |
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132 ``sine.eps``. |
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133 |
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134 {{{ switch to next slide, solution 1 }}} |
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135 |
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136 {{{ Switch focus to IPython interpreter }}} |
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137 |
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138 Now, We will save the plot using the function ``savefig`` :: |
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139 |
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140 savefig('/home/fossee/sine.eps') |
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141 |
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142 {{{ Switch focus to file browser window }}} |
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143 |
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144 Now let us go to ``/home/fossee`` and see the new file created. |
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145 |
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146 {{{ Highlight the file sine.eps with a single mouse click for 2 |
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147 seconds and then double click and open the file }}} |
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148 |
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149 Yes! the new file ``sine.eps`` is here. |
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150 |
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151 {{{ switch to next slide, exercise 2 }}} |
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152 |
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153 Now you may try saving the same in pdf, ps, svg formats. |
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154 |
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155 {{{ Switch to summary slide }}} |
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156 |
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157 This brings us to the end of this tutorial, in this tutorial we |
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158 learned to save plots using the function ``savefig()``. Saving the |
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159 plots in different formats and locating the files in the file system. |
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160 |
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161 {{{ switch to Thank you slide }}} |
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162 |
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163 Thank you! |