title: How can I detect if trend is increasing or decreasing in time series?
body: <p>I have few weeks data with units sold given</p>
  <pre class="lang-py prettyprint-override"><code>xs[weeks] = [1,2,3,4]
  ys['Units Sold'] = [1043,6582,5452,7571]
  </code></pre>
  <p>from the given series, we can see that although there is a drop from xs[2] to xs[3] but overall the trend is increasing. How to detect the trend in small time series dataset.</p>
  <p>Is finding a slope for the line is the best way? And how to calculate slope angle of a line in python?</p>