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| 21 | <h1><a class="anchor" name="itfile">Writing and reading data from files </a></h1>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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| 22 | <div class="fragment"><pre class="fragment"><span class="preprocessor">#include <itpp/itcomm.h></span> |
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| 23 | |
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| 24 | <span class="keyword">using namespace </span>itpp; |
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| 25 | |
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| 26 | <span class="keywordtype">int</span> main() |
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| 27 | { |
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| 28 | <span class="comment">// Declare the it_file class</span> |
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| 29 | it_file ff; |
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| 30 | |
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| 31 | <span class="comment">// Open a file with the name "it_file_test.it"</span> |
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| 32 | ff.open(<span class="stringliteral">"it_file_test.it"</span>); |
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| 33 | |
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| 34 | <span class="comment">// Create some data to put into the file</span> |
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| 35 | vec a = linspace(1, 20, 20); |
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| 36 | |
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| 37 | <span class="comment">// Put the variable a into the file. The Name("a") tells the file class</span> |
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| 38 | <span class="comment">// that the next variable shall be named "a".</span> |
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| 39 | ff << Name(<span class="stringliteral">"a"</span>) << a; |
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| 40 | |
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| 41 | <span class="comment">// Force the file to be written to disc. This is useful when performing</span> |
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| 42 | <span class="comment">// iterations and ensures that the information is not stored in any cache</span> |
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| 43 | <span class="comment">// memory. In this simple example it is not necessary to flush the file.</span> |
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| 44 | ff.flush(); |
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| 45 | |
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| 46 | <span class="comment">// Close the file</span> |
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| 47 | ff.close(); |
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| 48 | |
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| 49 | <span class="comment">// Exit program</span> |
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| 50 | <span class="keywordflow">return</span> 0; |
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| 51 | } |
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| 52 | </pre></div><p> |
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| 53 | 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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| 54 | <div class="fragment"><pre class="fragment">itload(<span class="stringliteral">'it_file_test.it'</span>) |
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| 55 | figure(1); clf; |
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| 56 | plot(a) |
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| 57 | </pre></div><p> |
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| 58 | 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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| 59 | 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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| 60 | <div class="fragment"><pre class="fragment"></pre></div><p> |
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| 61 | Here is the output of the program:<p> |
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| 62 | <div class="fragment"><pre class="fragment"> |
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| 63 | 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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| 64 | </pre></div> </div> |
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