What's a good, generic name for chart of things by time of day?

We're creating a chart showing traffic by time of day over a given period. So the y-axis is traffic, the x-axis is midnight, 1am, 2am, etc. It could also be days of the week. What's the generic name for this type of chart? I've come up with "cycle chart". Is that the standard? Is there one?

Update:

Just to add a bit more clarity, what's being shown in the top chart is not one day, it's an aggregation of many days. E.g. over the last month, 6am has on average been lower than noon. Similarly, in the bottom chart, over the last year, traffic dips on Saturdays.

• oh, great. now the sketch is there. :) – sprugman Mar 18 '11 at 18:21
• 'Periodic chart'? – onestop Mar 18 '11 at 18:50
• @onestop: that's a decent alternative to "cyclic". If you turn the comment into an answer, I might give it to you. – sprugman Mar 18 '11 at 20:52
• An aside: Sometimes it is better to plot this kind of chart around a circle. For example, there might be an interesting pattern from 10pm to 2am, but, the way that your chart is cut at midnight, you might not notice this pattern. See here: stackoverflow.com/questions/2076370/… – Charlie Mar 18 '11 at 22:35
• @Charlie an alternative that is often easier to both plot and read is to repeat part of the data and plot a bit more than a complete period, e.g. to plot over 30 hours from midnight to midnight and on to 6am, so the info from midnight to 6am appears twice - much as New Zealand or Alaska appear twice on some maps. I got this idea via Stata guru Nick Cox but I can't find the ref at present. Tukey (1972) favoured two complete cycles. – onestop Mar 19 '11 at 8:21

Nick Cox (Stata Journal 2006, p403) calls this sort of plot a 'cycle plot', but notes that:

Cycle plots have been discussed under other names in the literature, including cycle-subseries plot, month plot, seasonal-by-month plot, and seasonal subseries plot.

(followed by a load of refs to textbooks and papers)

Many of these are clearly specific to seasonality, i.e. periods of one year. I still like the suggestion of 'periodic plot/chart' that I made in a comment to the question, but it appears the questioner's original suggestion of 'cycle plot/chart' is in fact the more standard generic term.

• Even though we wound up going with histogram in case we decide to do other kinds of similar charts that aren't time related, I think this is the most direct answer to the question that I asked. (We're actually using histogram/time, but maybe I'll change it to histogram/cycle....) – sprugman Mar 19 '11 at 16:14

What you've illustrated is a time series column (or bar) graph. The two graphs are of differing time resolution or differing time aggregation.

There may be industry specific terms for these types of charts. In finance, for example, the open-high-low-close chart is a very common time series plot:

When the x axis is time, as in your example, it's often common to illustrate the points as a line graph, instead of bars/columns. The reason for this is to put the visual emphasis on the change from one period to the next.

You might also consider graphing period-over-period. For example a year-over-year would show how the numbers for a given month (typically, although could be month or day) compare to the numbers of the prior year for the same month.

But I realize your question was about naming, not all the other cool graphs you can do ;)

• The point of the question seems to be that the x-axis summarizes a periodic or cyclic variable. – whuber Mar 18 '11 at 19:40
• @whuber: yup! (thanks for the detailed answer, though, JD) – sprugman Mar 18 '11 at 20:28
• doh! thanks @whuber, I didn't realize that. – JD Long Mar 18 '11 at 20:54

I'd suggest "diurnal" or "circadian" rhythm chart. For weekly, the latter would be "circaseptan", "circamensual" for "monthly", and "circannual" for "yearly".

• those are all cool, but I was looking for something for the whole class of charts. We went with histogram.... – sprugman Mar 19 '11 at 16:11

The type of chart you've drawn is known as a Histogram http://en.wikipedia.org/wiki/Histogram

• Being picky: A histogram never has blank spaces between the bars. When it does it is called a bar chart – Ralph Winters Mar 18 '11 at 19:27
• @os @Ralph A histogram represents probability (or frequency) by means of graphical area, whereas a "bar chart" (which is what we're looking at here) uses length. Of course histograms can have blank spaces between bars, when there's no probability or frequency there! – whuber Mar 18 '11 at 19:38
• I take back my earlier comment. Given what I now realize from the discussion, this could be a histogram showing frequency by time or day buckets. – JD Long Mar 18 '11 at 20:56
• as I said on Owe's answer, I think technically, this is correct, but a name that indicates the relationship to time would be nice. – sprugman Mar 18 '11 at 21:57
• A histogram displays the distribution of a continuous variable. A bar chart displays the distribution of a discrete variable. – hadley Mar 19 '11 at 17:15

Short, simple, descriptive: time series plot.

Edit: In light of the discussion, I'd vote for histogram as well. At least, thats the generic name for this kind of chart, where the hours of the day are a natural division of stacks.

• to me, "time series" implies either a cycle, or linear time. I'm interested in something specific to cyclic data. – sprugman Mar 18 '11 at 20:28
• Seems I misunderstood your question - so the data is aggregated over the hours of a day, or or the days of the week for a number of days or weeks? In that case it is a kind of histogram. – Owe Jessen Mar 18 '11 at 20:36
• hmm... I think you're correct (looking at the wiki entry on histogram), but ideally something specific to time would be better. – sprugman Mar 18 '11 at 20:45

Your charts are a diurnal hourly-average bar chart, and a one-week daily-average bar chart, respectively.