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| 67 | <h1><a class="anchor" id="itfile">Writing and reading data from files </a></h1><p>Here we will use the <code>it_file</code> class to store some data. The program <code>write_it_file.cpp</code> looks as follows:</p> |
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| 68 | <div class="fragment"><pre class="fragment"><span class="preprocessor">#include <itpp/itcomm.h></span> |
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| 69 | |
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| 70 | <span class="keyword">using namespace </span>itpp; |
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| 71 | |
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| 72 | <span class="keywordtype">int</span> main() { |
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| 73 | <span class="comment">// Declare the it_file class</span> |
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| 74 | it_file ff; |
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| 75 | |
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| 76 | <span class="comment">// Open a file with the name "it_file_test.it"</span> |
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| 77 | ff.open ( <span class="stringliteral">"it_file_test.it"</span> ); |
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| 78 | |
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| 79 | <span class="comment">// Create some data to put into the file</span> |
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| 80 | vec a = linspace ( 1, 20, 20 ); |
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| 81 | |
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| 82 | <span class="comment">// Put the variable a into the file. The Name("a") tells the file class</span> |
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| 83 | <span class="comment">// that the next variable shall be named "a".</span> |
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| 84 | ff << Name ( <span class="stringliteral">"a"</span> ) << a; |
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| 85 | |
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| 86 | <span class="comment">// Force the file to be written to disc. This is useful when performing</span> |
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| 87 | <span class="comment">// iterations and ensures that the information is not stored in any cache</span> |
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| 88 | <span class="comment">// memory. In this simple example it is not necessary to flush the file.</span> |
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| 89 | ff.flush(); |
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| 90 | |
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| 91 | <span class="comment">// Close the file</span> |
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| 92 | ff.close(); |
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| 93 | |
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| 94 | <span class="comment">// Exit program</span> |
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| 95 | <span class="keywordflow">return</span> 0; |
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| 96 | } |
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| 97 | </pre></div><p>When you run this program you will obtain a file called <code>it_file_test.it</code> in your current directory. You can read the file into Matlab/Octave to view the data by using the following commands:</p> |
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| 98 | <div class="fragment"><pre class="fragment">itload(<span class="stringliteral">'it_file_test.it'</span>) |
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| 99 | figure(1); clf; |
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| 100 | plot(a) |
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| 101 | </pre></div><p>Note: Make sure that <code>$PREFIX/share/itpp</code> is in your Matlab/Octave path and that you run the code above from the directory where <code>it_file_test.it</code> is located (<code>$PREFIX</code> is the IT++ installation prefix; <code>/usr/local</code> by default).</p> |
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| 102 | <p>The IT++ program <code>read_it_file.cpp</code> that reads the file and prints its content can look like this:</p> |
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| 103 | <div class="fragment"><pre class="fragment"></pre></div><p>Here is the output of the program:</p> |
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| 104 | <div class="fragment"><pre class="fragment"> |
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| 105 | a = [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20] |
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| 106 | </pre></div> </div> |
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