def get_rod(da_peak_values, da_peak_times, da_eos_values, da_eos_times):
    """
    Takes four xarray DataArrays containing the peak season values (either pos or 
    mos) and times (day of year), and end of season (eos) values and times (day 
    of year). The rate of decrease (rod) is calculated as the ratio of the difference 
    in peak and eos for vege values and time (day of year) per pixel. 

    Parameters
    ----------
    da_peak_values: xarray DataArray
        An xarray DataArray type with an x and y dimension (no time). Each pixel is the 
        vege value detected at either the peak (pos) or middle (mos) of season.
    da_peak_times: xarray DataArray
        An xarray DataArray type with an x and y dimension (no time). Each pixel is the 
        time (day of year) value detected at either the peak (pos) or middle (mos) of 
        season.
    da_eos_values: xarray DataArray
        An xarray DataArray type with an x and y dimension (no time). Each pixel is the 
        vege value detected at end of season (eos).
    da_eos_times: xarray DataArray
        An xarray DataArray type with an x and y dimension (no time). Each pixel is the 
        time (day of year) detected at end of season (eos).

    Returns
    -------
    da_roi_values : xarray DataArray
        An xarray DataArray type with an x and y dimension (no time). Each pixel is the 
        rate of decrease value detected between the eos and peak values/times across the 
        timeseries at each pixel. The values in rod represents rate of vege decline.
    """
    
    # notify user
    print('Beginning calculation of rate of decrease (rod) values (times not possible).')   

    # get abs ratio between the difference in peak and eos values and times
    print('> Calculating rate of decrease (rod) values.')
    da_rod_values = abs((da_eos_values - da_peak_values) / (da_eos_times - da_peak_times))
    
    # convert type
    da_rod_values = da_rod_values.astype('float32')
    
    # rename vars
    da_rod_values = da_rod_values.rename('rod_values')

    # notify user
    print('> Success!\n')
    
    return da_rod_values