11.56 Scatter Plot Smooth Gam


ds %>%
  filter(location=="Canberra") %>%
  ggplot(aes(x=date, y=max_temp)) +
  geom_point(shape=".") +
  geom_smooth(method="gam", formula=y~s(x, bs="cs")) +
  labs(x=vnames["date"], y=vnames["max_temp"])

This scatter plot of x=date against y=max_temp shows a pattern of seasonality over the dataset and a trend line over the period of the dataset.

The scatter plot is again created using ggplot2::geom_point(). Typical of scatter plots of big data there will be many overlaid points. To reduce the impact the points are reduced to a small dot using shape=".".

An additional layer of a smooth fitted curve, using ggplot2::geom_smooth(), is added. The dataset has many points and so a smoothing method recommended is method="gam" which will automatically be chosen if not specified but with a message to that effect. The formula specified using formula= is also the default for method="gam".

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