4.6 Figure 4.21 shows the biyearly smoothed (12-month moving average) number of sunspots from June 1749 to December 1978 with n = 459 points that were taken twice per year; the data are contained in sunspotz. With Example 4.7 as a guide, perform a periodogram analysis identifying the predominant periods and obtaining confidence intervals for the identified periods. Interpret your findings. 4.7 The levels of salt concentration known to have occurred over rows, corresponding to the average temperature levels for the soil science are in salt and sal temp. Plot the series and then identify the dominant frequencies by performing separate spectral analyses on the two series. Include confidence intervals for the dominant frequencies and interpret your findings