help for ^barplot^

Bar plot --------

^barplot^ yvarlist xvar [^if^ exp] [^in^ range] [ ^, w^idth^(^string^) b^ase^(^string^) m^onths ^join^ graph_options ]

Description -----------

^barplot^ produces a plot of the variables in yvarlist against xvar. Each variable in yvarlist is plotted as a series of unshaded bars rising above or falling below one or more base lines. The height of each bar is given by the y variable, the width via the width option, the base via the base option and the horizontal centre of each bar by xvar.

^barplot^ could be used, for example, to

plot monthly totals or other time series as a series of touching bars, positive and negative values shown upwards and downwards (rainfall/evaporation, profit/loss, income/expenditure)

show histograms, especially those with more than 50 bins (classes) or unequal bin widths (class intervals), or with unshaded bars

show the difference between two histograms as a series of bars that may be positive or negative

show J.W. Tukey's rootograms, with the square root of frequencies on the y axis.

Note especially in the case of histograms or rootograms that the frequencies must be calculated beforehand.

Through the ^width()^ option, ^barplot^ could be used to produce overlapping or underlapping bars, if desired for some reason.

Options -------

^width(^string^)^ specifies how the widths of the bars are determined. ^width(^widthvar^)^ specifies that they are given by widthvar. ^width(^#^)^ specifies that they are constant and equal to #. The default is ^width(1)^.

^base(^string^)^ specifies how the bases of the bars are determined. ^base(^basevar^)^ specifies that they are given by basevar. ^base(^#^)^ specifies that they are constant and equal to #. The default is ^base(0)^.

^months^ without ^xlabel( )^ automatically produces ^xla(1,2,3,4,5,6,7,8,9,10,12)^.

^join^ specifies that bars that do not touch will be joined, i.e. connected by fragments of a baseline. Separate bars usually look better on histograms containing gaps (bins with zero frequency). Joined bars often look better with time series plots.

graph_options are options allowed with ^graph, twoway^, other than ^symbol^ and ^connect^, which are set to ^i^ and ^L^ for each y variable, and ^xlabel^ by itself. Note that these options do not include ^shading^.

Examples --------

. ^barplot pop age^ . ^barplot rain month, mon^ . ^barplot males females age^

Histogram from data:

. ^genfreq r if r > 0, w(1) b(Br) f(Fr)^ . ^barplot Fr Br, w(1)^

OR . ^histplot r if r > 0, w(1)^

Histogram from data, discrete variables:

. ^egen freq = count(rep78), by(rep78)^ OR . ^genfreq rep78, fg(freq)^

. ^barplot freq rep78, w(0.5) yla xla(1,2,3,4,5)^

Histogram with unequal bin widths (Snedecor and Cochran, 1989, p.19):

. ^input centre width freq^ . ^112.5 25 38^ . ^137.5 25 27^ . ^162.5 25 15^ . ^187.5 25 11^ . ^250 100 4^ . ^350 100 4^ . ^450 100 1.8^ . ^550 100 2^ . ^700 200 1.2^ . ^900 200 0.2^ . ^barplot freq centre, w(width) l2(Frequency per 25000)^ ^b2(Population in 000) yla^

Superimposed histograms for different groups:

. ^genfreq length, w(5) bg(Blength) fg(Flength) by(foreign)^ . ^gen Flengthf = Flength if foreign^ . ^gen Flengthd = Flength if !foreign^ . ^barplot Flengthf Flengthd Blength, w(5)^

Normal and inverted histograms for different groups: . ^gen nFlf = -Flength if foreign^ . ^barplot nFlf Flengthd Blength, w(5)^

Separate histograms for different groups:

same colour: . ^barplot Flength Blength, w(5) by(foreign)^

different colours: . ^barplot Flengthf Flengthd Blength, w(5) by(foreign)^

Superimposed histograms for different variables:

. ^genfreq n, w(0.5) bg(Bn) fg(Fn)^ . ^genfreq x, w(0.5) bg(Bx) fg(Fx)^ . ^stack Bx Fx Bn Fn, into(B F) wide clear^ . ^barplot Fx Fn B, w(0.5)^

Separate histograms for different variables: . ^barplot Fx Fn B, w(0.5) by(_stack)^

Author ------

Nicholas J. Cox, University of Durham, U.K. n.j.cox@@durham.ac.uk

Also see --------

On-line: help for @graph@, @spikeplt@ (if installed), @genfreq@ (if installed), @histplot@ (if installed)