Converting time vectors into Julian days
<p>I have a .txt file in which the second column represents the measuring time in seconds (starting date of measurements is 04/01/15) during 367 days (end date of measurements is 04/01/16). The third and so on are measured variables. </p>

<p>In my analysis I need to have this second column in Julian days (when dealing with this type of date I usually use as "origin" 01/01/1992) in order to assess with other variables in other files that have already the date in Julian time. I could also use the calendar date instead if I had it!</p>

<p>Example of the file:</p>

<p>(First day)</p>

<pre><code>091.00000   0.00    102.63  16.79   81.40   5.07    144.20  0.00
091.00069   60.00   102.63  16.80   81.30   5.86    136.00  0.00
091.00139   120.00  102.63  16.75   81.20   2.46    144.20  0.00
</code></pre>

<p>(...)</p>

<pre><code>091.99931   86340.00    102.53  17.09   82.60   1.60    117.00  0.00
</code></pre>

<p>(Second day)</p>

<pre><code>092.00000   0.00    102.53  16.96   82.60   1.56    115.00  0.00
092.00069   60.00   102.53  16.87   82.90   1.38    114.70  0.00
092.00139   120.00  102.53  17.01   82.90   1.13    110.30  0.00
</code></pre>

<p>(...)</p>

<pre><code>092.99931   86340.00    102.44  17.38   87.10   1.75    116.00  0.00
</code></pre>

<p>This happens for all days during the entire 367 days (corresponding to a total of 526970 measurements) and I have this all together in one file. There might be missing data recording, so I can use missing values (NA) in those gaps.</p>

<p>I'm using R.  </p>