Ryan's Tech Blog

Another productive afternoon:

This is the start of axes. The internals are getting very, very messy, but I really like the result. Here’s the code used to create this:

(defun line-chart-with-axis-labels ()  
  "draws a simple line chart"
  (let* ((seriesA (make-instance 'series
				 :label "SeriesA"
					;data expressed as a list (x y) pairs
				 :data '((-1 -2) (0 4) (1 5) (4 6) (5 -3))))
	 (seriesB (make-instance 'series
				 :label "SeriesB"
				 :data '((-1 4) (0 -2) (1 6) (5 -2) (6 5))))
	 (y-axis (make-instance 'axis
				:label "widgets"
				:label-formatter #'(lambda (x-val)
						     (format nil "~$" x-val))))
	 (chart (make-instance 'line-chart
			       :width 400
			       :height 300
			       :background '(.7 .7 .7)
			       :series (list seriesA seriesB)
			       :y-axis y-axis)))
    (render-chart chart "line-chart-with-axis-labels.png")))

I predict adding X axes will be very similar to adding the Y axis, and then I’ll be looking more seriously at spending time to make good docs and releasing this back to the community. The API is getting a little dense, too, but that should be pretty easy to simplify, and I have a few ideas on how to do that.