To determine the amount of increase or decrease
in 100 years, we have adopted least square linear
fit of the data. The advantage of linear regression
is that it provides an estimate of slope, confidence
interval and quantifies goodness of fit. However, it
does not handle missing data and may be greatly
affected by outliers and cyclic data. As mentioned
earlier in our study we have removed the effect
of missing days observation by dividing the actual
annual frequency with actual number of observation
days of that year and then multiplying by the
number of days of that year