Introduction to Statistics (MAT/SST 115.03 2008S)

Histograms


Quick Examples

hist(vector,
  breaks=seq(from=min,to=max,by=step)
  axes=FALSE,
  main="Title"
  xlab="Label of X Axis"
)
axis(1, seq(from=min,to=max,by=step))

Note that you want to use different sequences for the breaks and the axis. In some models (such as that used in our book), the breaks usually come between values, which means it will be helpful if they have a fractional component. In contrast, you want the tick marks to be in the middle of each bar. For example, if we wanted to deal with values between 0 and 100, grouped into sections of 5, we might use

hist(vector,
  breaks=seq(from=-2.5,to=102.5,by=5),
  axes=FALSE,
  main="Title"
  xlab="Label of X Axis"
)
axis(1, seq(from=0,to=100,by=5))

Some Notes

Histograms provide a visual way to summarize data in cases in which you want to group nearby values. In many ways, they resemble dot plots, but they use broader categories for the dots.

You make histograms with the hist function>. It takes as its primary parameter a vector of values. (As is the case with dotplots, the hist function will tally the values for you.)

hist(vector)

If you give R no other information on the histogram, it chooses the breaks for you. Most of the time, you want to choose the breaks yourself.

Creative Commons License

Samuel A. Rebelsky, rebelsky@grinnell.edu

Copyright (c) 2007-8 Samuel A. Rebelsky.

This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA.