DynamicImages2

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Revision as of 22:42, 14 February 2008

Adding Labels, Lines and Points to Dynamic Graphs: PG Code Snippet

This code snippet shows the essential PG code to add labels, lines and points to dynamically generated graphs. Note that these are insertions, not a complete PG file. This code will have to be incorporated into the problem file on which you are working.

Problem Techniques Index

PG problem file Explanation
  loadMacros("PGgraphmacros.pl");

We have no required additions to the tagging and description section of the file, and we obviously need to include PGgraphmacros.pl to do dynamic graphs.

  # a graph object
  $gr = init_graph(-1,4,-1,4,axes=>~[0,0],grid=>[5,5]);
  # plot a function
  add_functions($gr,
  "4-3*e^(-x) for x in <-1,4> using color:blue and weight:2");

  # add a label
  $gr->lb( new Label(0.25,3.25,'(0,3)',
  'black','center','center'));

  # a line
  $gr->moveTo(-1,1);
  $gr->lineTo(4,1,'black');

  # and a point
  $gr->stamps( closed_circle(0,3,'blue') );

In the initialization part of the file, we define a [dynamically generated graph|DynamicImages]. Then we can add labels, lines and points to the graph.

To add labels, we use the lb method of the graph object. The argument is a new Label object, defined by an x-coordinate, y-coordinate, label text, color, and justification. The justification can be left, center or right for the left-to-right justification, and top, center or bottom for the top-to-bottom justification.

Lines are added by moving the graph "cursor" to a point and then drawing a line to a new point.

And we add points by using the stamps method of the graph object. We've added a closed circle here; as might expect, open_circles are also supported.

  BEGIN_TEXT
  \{ image( insertGraph($gr) ) \}
  END_TEXT

And the graph is inserted in the text portion of the problem as we'd expect any static or dynamic image to be.

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