Google Charts API - Column patterns and "TimeOfDay" data type

Question

I'm working with the Google Charts API to create a graph of a student's test-taking performance. On the X axis, the graph shows the days of the week. On the Y axis, the graph shows how long the student spent taking the exam. (The goal is for teachers to see if the student speeds up). However, I have a problem:

My data is in the timeofday format, and I'm providing values to the chart as time durations using the Google Charts [HH,MM,SS,MSEC] format. When the chart renders, the Y axis is printed as "HH:MM:SS". I'd really like to customize that because the seconds are pretty useless and it looks messier than I'd like.

The Charts API says you can specify a "pattern" for a column, and I've specified "HH:MM". However, that doesn't seem to take effect at all. Anybody have experience formatting timeofday in Google Charts and know how to do this?

Answer 1

The format is buried deep in the API documentation. (http://code.google.com/apis/chart/interactive/docs/reference.html). It is about quarter way down, it says:

If the column type is 'timeofday', the value is an array of four numbers: [hour, minute, second, milliseconds].