@node Histogram, History, Help, Commands

@iftex
@syntax Histogram.
@end iftex
@example
Syntax: HISTOGRAM WORD1 WORD2 [ IF (expr) ]
@end example
@pindex Histogram

HISTOGRAM connects the points in vectors @code{WORD1} and @code{WORD2} as
a histogram.
The @code{i}th bin of the histogram is taken to run from
@code{(x[i-1] + x[i])/2} to @code{(x[i] + x[i+1])/2};
for the case of equally spaced x-values, this reduces
to saying that the x values are the bin centres.

If the IF clause is present, only use those points for which @code{expr} (see
the section on vector arithmetic) is true (i.e. non-zero).

In fact, either or both of the @code{WORD}s may be replaced by
`parenthesised expressions', i.e. expressions in parentheses. For example,
@example
HISTOGRAM x (2 + y)
@end example
@noindent
to plot x against @i{2 + @r{y}}.
There is a macro @code{barhist} for drawing bar charts.
See Arithmetic for how to convert vectors of data into histograms, and
@code{SHADE} for how to shade them.