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JSPlot Documentation: The plotting canvas

  1. The plotting canvas
  2. Plotting data
  3. Plotting functions
  4. Vector graphics
  5. Graph plotting styles
  6. Graph options
  7. Graph axis options
  8. Vector graphics objects

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JSPlot_Canvas class: API reference

Instances of the JSPlot_Canvas class are used to create a new drawing canvas onto which to add charts and other vector graphics objects. Once a new canvas has been populated, call the renderToCanvas method to render its contents onto an HTML5 <canvas> element. Alternatively, the renderToPNG and renderToSVG methods render the canvas to PNG and SVG files respectively.

my_canvas = new JSPlot_Canvas(list_of_objects, settings);

Argument Allowed values Description
list_of_objects Associative array

An associative array of items to put on the canvas. These should be instances of the JSPlot_Graph, JSPlot_Arrow, JSPlot_Circle, JSPlot_Rectangle or JSPlot_Text classes.

The key associated with each member of the associated array may subsequently be used to remove that item from the canvas, using the JSPlot_Canvas instance's removeItem method. Additional items can be added to the canvas using the addItem method.

settings Associative array An associative array of configuration options. Allowed key values are listed below.

Allowed configuration parameters are as follows:

Field Allowed values Description
allow_export_png boolean Choose whether a button should appear beneath the plot, inviting the user to download a PNG copy of the canvas.
allow_export_svg boolean Choose whether a button should appear beneath the plot, inviting the user to download a SVG copy of the canvas.
allow_export_csv boolean Choose whether a button should appear beneath the plot, inviting the user to download a copy of the data plotted on the first graph on the canvas, in CSV format.

Once instantiated, a JSPlot_Canvas instance offers the following methods:

Method Arguments Description
configure settings (associative array) Update the settings for this canvas. settings should be an associative array, with the same keys as listed above.
renderToCanvas target_element (HTML element) Render the drawing canvas onto an HTML5 drawing canvas. The drawing canvas is resized to accommodate the objects on the JSPlot canvas.
addItem name (string)
item (canvas object)

Add an object to the drawing canvas. The name should be a unique string which can be used to subsequently remove the item by calling the removeItem method on the JSPlot_Canvas instance.

The item argument should be an instance of the JSPlot_Graph, JSPlot_Arrow, JSPlot_Circle, JSPlot_Rectangle or JSPlot_Text classes.

removeItem name (string) Remove a named object from the drawing canvas.
renderToPNG page_width (number) Render the contents of the canvas to a PNG file, and redirect the web browser to show the contents of that PNG file. If specified, the argument page_width should indicate the width of the PNG file in pixels.
renderToSVG page_width (number) Render the contents of the canvas to a SVG file, and return the contents of the SVG file as a string. If specified, the argument page_width should indicate the width of the SVG file in pixels.
renderToCSV None Render the data shown on the first graph on the canvas into CSV, and return the contents of that CSV file as a string.

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