The plot shows elements of a decomposition of weekly log-mortality rate for age-group 65+ in England and Wales from January 2010 to November 2017.
A Generalised Additive Model (GAM) was used to extract a smooth seasonal component of mortality (plotted in green), a linear trend (not displayed), and any smooth deviations from this trend (blue), on top of the average seasonal trend. The effects of public holidays were controlled for using fixed effects. Weekly exposures were obtained by interpolation between midyear population estimates. For 2017, the 2016-based ONS National Population Projections were used to approximate the relevant exposures.
Of particular interest is the extreme flu season in the early part of 2015.
Data was obtained from the UK Office of National Statistics.
The R package mgcv was used to fit the GAM.
The visualisation is done in d3.js, using ideas and code from two examples: this polar plot and this d3 example including a slider. The code for these examples was provided under GPL 3.0 and MIT licenses respectively.