Programming Web Graphics with Perl and GNU Softwar

Name

plot( ) — generate a GIF from data

Synopsis

GIFgraph::plot(\@data)

The plot( ) method will take a data set, plot it according to the type of graph object and the values of the attributes that have been set, and return a scalar containing the GIF data. This function is used most often for plotting a graphic to STDOUT in CGI applications. Note that the data set is passed as a list of references to arrays; the first array in the list represents the values for the x axis, and each array after that represents a different set of y values to be plotted. For example, the following data will generate a graph with the month names on the x axis and two sets of numbers plotted against the y axis:

@data = (
        [ qw(JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC) ],
        [ 5,  8,  24,  32,  12,  18,  11,  21,  22,  9,  29,  16 ],
        [ 6.5,  12.8,  31.7,  3,  9,  15,  14.8,  21.2,  7,  9.9, 10,  7.2 ]
        );
$graph->plot(\@data);

If the arrays are not set up correctly (if, for example, the arrays are not all the same length), Perl will complain with a “length misfit” error. The data sets may be padded with undef values if the values are not to be plotted.