# Does the y-axis of a histogram have to be frequency?

The definition of a histogram is a graph in which the x-axis is a quantitative variable split into bins, and the y-axis is the frequency. However, if we want to graph some other property of the bins (not the frequency), is the resulting graph still a histogram? Or is it considered a bar graph?

For example, say the x-axis is the age of the residents of a city, split into bins of size 10 years. We graph the total income of the residents in each bin. (The y-axis is income.) Is the resulting graph a histogram or a bar graph or something else? (I read that the bar graph is supposed to have categorical, not quantitative, variables on the x-axis.)

• When you plot averages it's a regressogram; in your case (where it's total rather than average) you might call it a graph of binned total income by age – Glen_b -Reinstate Monica Sep 15 '16 at 21:55
• This appears to be a nonstandard definition of "histogram." The usual definition is that histograms use areas (not lengths or heights) to represent frequencies or densities. (Google and Wikipedia are clear about that. Also see our threads on histograms, such as stats.stackexchange.com/questions/24568, where the distinction is particularly important.) Your definition describes a bar graph of frequency. – whuber Sep 15 '16 at 21:56