title: How do you retrieve the min and max of time series data
body: <p>I want to use matplotlib to shade between the minimum and maximum values of my timeseries data. Here is a sample of the data. How do i retrieve the min and max. (note that time given below is in string format but i have the time in seconds from previous day 00:00:00 so i have time as 5902761,5902770)</p>
  
  <p>e.g </p>
  
  <pre><code>index       time            value
     1    08:00:00         100
     2    08:00:01         100
     3    08:00:01         101
     4    08:00:02         100
     5    08:00:02         102
     6    08:00:02         101
  </code></pre>
  
  <p>What i want is the following</p>
  
  <pre><code>index       time        min_value   max_value
     1      08:00:00         100         100
     2      08:00:01         100         101
     3      08:00:02         100         102
  </code></pre>