What I meant by saying "poor" for GoogleVis API was: it has very limited capability of drawing genuine statistical graphics, e.g. histogram/density curve, boxplot, scatter plot with regression line or LOWESS curve, not to mention sunflower scatter plot, conditional density plot, contour plot/lines, mosaic plot, ...
To the general audience, the bar/line/pie chart are much more common and easy to understand, but what they reveal is just the original data (or numbers) -- little summary, no statistical inference and hence limited information.
For your question, I haven't found a good API for (general) data visualization yet. There might be good ones for specific tasks, I think.
Originally posted on 2009-06-11 16:07:04