Douglas A. Campbell

I suggest (re)moving the final section 'Arranging plots', installing and using 'patchwork' to arrange multiple ggplot objects. It seems beyond the scope of introducing data visualization and would be better...

A common issue is plotting data versus elapsed, vs. absolute, time or date. A further challenge suggestion: 2. Generate a new column, days_elapsed, by subtracting the lowest value of surveys$date...