title: Interpolation in R
body: <p>I have hourly time series and would like to interpolate sub-hourly values like every 15 min. Linear interpolation will do. But if there is any way to specify Gaussian, Polynomial, that would be great.</p>
  
  <p>For example if I have</p>
  
  <p>a&lt;-c(4.5,7,3.3) which is the first three hour data. How can I get 15 min sub-hourly data, total of 9 values in this case? I have been using approx function and studying zoo package and still don't know how I can do it. Thank you very much!</p>