If autoscale is in e ect, it selects the xrange from the data rather than the steps, so the end points will appear only half as wide as the others. See also

steps demo.

histeps is only a plotting style; gnuplot does not have the ability to create bins and determine their population from some data set.

Histograms

The histograms style is only relevant to 2D plotting. It produces a bar chart from a sequence of parallel data columns. Each element of the plot command must specify a single input data source (e.g. one column of the input le), possibly with associated tic values or key titles. Four styles of histogram layout are currently supported.

set style histogram clustered {gap <gapsize>}

set style histogram errorbars {gap <gapsize>} {<linewidth>} set style histogram rowstacked

set style histogram columnstacked

The default style corresponds to set style histogram clustered gap 2. In this style, each set of parallel data values is collected into a group of boxes clustered at the x-axis coordinate corresponding to their sequential position (row #) in the selected data le columns. Thus if <n> datacolumns are selected, the rst cluster is centered about x=1, and contains <n> boxes whose heights are taken from the rst entry in the corresponding <n> data columns. This is followed by a gap and then a second cluster of boxes centered about x=2 corresponding to the second entry in the respective data columns, and so on. The default gap width of 2 indicates that the empty space between clusters is equivalent to the width of 2 boxes. All boxes derived from any one column are given the same ll color and/or pattern (see set style ll (p. 147)).

Each cluster of boxes is derived from a single row of the input data le. It is common in such input les that the rst element of each row is a label. Labels from this column may be placed along the x-axis underneath the appropriate cluster of boxes with the xticlabels option to using.

The errorbars style is very similar to the clustered style, except that it requires additional columns of input for each entry. The rst column holds the height (y value) of that box, exactly as for the clustered style.

The appearance of the error bars is controlled by the current value of set bars and by the optional <linewidth> speci cation.

Two styles of stacked histogram are supported, chosen by the command set style histogram frowstackedjcolumnstackedg. In these styles the data values from the selected columns are collected into stacks of boxes. Positive values stack upwards from y=0; negative values stack downwards. Mixed positive and negative values will produce both an upward stack and a downward stack. The default stacking mode is rowstacked.

The rowstacked style places a box resting on the x-axis for each data value in the rst selected column; the rst data value results in a box a x=1, the second at x=2, and so on. Boxes corresponding to the second

and subsequent data columns are layered on top of these, resulting in a stack of boxes at x=1 representing the rst data value from each column, a stack of boxes at x=2 representing the second data value from each column, and so on. All boxes derived from any one column are given the same ll color and/or pattern (see set style ll (p. 147)).

The columnstacked style is similar, except that each stack of boxes is built up from a single data column. Each data value from the rst speci ed column yields a box in the stack at x=1, each data value from the second speci ed column yields a box in the stack at x=2, and so on. In this style the color of each box is taken from the row number, rather than the column number, of the corresponding data eld.

Box widths may be modi ed using the set boxwidth command. Box ll styles may be set using the set style ll command.

Histograms always use the x1 axis, but may use either y1 or y2. If a plot contains both histograms and other plot styles, the non-histogram plot elements may use either the x1 or the x2 axis.

This will produce a plot with clusters of two boxes (vertical bars) centered at each integral value on the x axis. If the rst column of the input le contains labels, they may be placed along the x-axis using the variant command

plot for [COL=2:4:2] 'file.dat' using COL:xticlabels(1)

plot for [COL=2:4:2] 'file.dat' using COL:COL+1

To plot the same data as a rowstacked histogram. Just to be di erent, this example lists the separate columns explicitly rather than using iteration.

set style histogram rowstacked

plot 'file.dat' using 2, '' using 4:xtic(1)

Note that the two examples just given present exactly the same data values, but in di erent formats.

Newhistogram

Syntax:

newhistogram {"<title>"} {lt <linetype>} {fs <fillstyle>} {at <x-coord>}

More than one set of histograms can appear in a single plot. In this case you can force a gap between them, and a separate label for each set, by using the newhistogram command. For example

set style histogram cluster

plot newhistogram "Set A", 'a' using 1, '' using 2, '' using 3, \ newhistogram "Set B", 'b' using 1, '' using 2, '' using 3

The labels "Set A" and "Set B" will appear beneath the respective sets of histograms, under the overall x axis label.

The newhistogram command can also be used to force histogram coloring to begin with a speci c color (linetype). By default colors will continue to increment successively even across histogram boundaries. Here is an example using the same coloring for multiple histograms

plot newhistogram "Set A" lt 4, 'a' using 1, '' using 2, '' using 3, \ newhistogram "Set B" lt 4, 'b' using 1, '' using 2, '' using 3

Similarly you can force the next histogram to begin with a speci ed llstyle. If the llstyle is set to pattern, then the pattern used for lling will be incremented automatically.

will position the second histogram to start at x=8.