What Is Required When Drawing A Time Series Plot

1.3. Time-series plots¶

Nosotros start off by because a plot about often seen in engineering applications: the time-series plot. The time-series plot is a univariate plot: it shows merely ane variable. It is a 2-dimensional plot in which one axis, the time-axis, shows graduations at an appropriate scale (seconds, minutes, weeks, quarters, years), while the other centrality shows the numeric values. Usually, the fourth dimension-axis is displayed horizontally, but this is not a requirement: some interesting assay can exist washed with fourth dimension running vertically.

Many statistical packages telephone call this a line plot, equally information technology can be used more often than not to display any sort of sequence, whether information technology is along time or some other ordering. The time-series plot is an first-class style to visualize long sequences of data. Information technology tells a visual story along the sequence axis, and the human being brain is incredible at absorbing this high density of data, locating patterns in the information such equally sinusoids, spikes, and outliers, and separating any dissonance from signal.

Here are some tips for effective time-series plots:

The software should accept horizontal and vertical zooming power. Once zoomed in, there must exist tools to whorl upward, down, left and right.
Ever label the x-centrality appropriately with (time) units that make sense.

This plot, found on the Internet, shows a computer's CPU temperature with time. There are several problems with the plot, but the cardinal issue here is the x-axis. This plot is probably the result of poor default settings in the software, but every bit yous will kickoff to realize, bad defaults are very common in about software packages. They waste your fourth dimension when you have to repeatedly modify the charts, peculiarly if you lot are but starting out with exploring the information. Proficient software volition sensibly characterization the time-based axis for yous.

When plotting more than one trajectory (a vector of values) against fourth dimension, information technology is helpful if the lines do not cross or jumble too much. This allows you lot to conspicuously see the relationship with other variables. The utilize of a second y-centrality on the right-hand side is helpful when plotting two trajectories, but when plotting iii or more than trajectories that are in the same numeric range, it is better to use several parallel axes.

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Using the same information as in the previous tip, a much improved visualization technique is to use sparklines to stand for the sequence of data.

Sparklines are pocket-sized graphics that carry a loftier density of information. The man eye is easily capable of arresting about 100 dots or points per linear centimeter and effectually 10000 points per foursquare centimeter. These sparklines convey the same amount of information every bit the previous plots and are like shooting fish in a barrel to consume on manus-held devices such every bit cellphones and tablet computing devices that are mutual in chemical plants and other engineering facilities. Read more about them from this hyperlink.
When plotting coin values over time (e.g. sales of your product over the past x years), adjust for aggrandizement effects by dividing past the consumer price alphabetize or an advisable factor. Distortions due to the time value of money tin exist very misleading, as this example of retail sales shows. For Canadians, here is a Canadian inflation calculator from the Banking company of Canada that can assistance you. For most countries you can almost certainly notice something similar from the land's national bank or a government function.
If y'all ever ask yourself, "Why are we being shown so little?" so you must asking more than data before and after the time period or current sequence shown. A typical example is stock-price data (see instance figure of Apple's stock). In that location are numerous graphical "lies" in magazines and reports where the plot shows a drastic modify in trend, merely in the context of prior data, that trend is a small aberration. Again, this brings into play the encephalon's remarkable ability to discern signal from noise, but to exercise this, our brains require context. Ask for the actress context, or wait for it, if not provided.