I mentioned LiveGraph in the post about my Arduino I2C sniffer sketch, but I wanted to go into a bit more detail about it, because it’s also really handy for visualizing data recorded with the Datalogger Shield. LiveGraph is nice because it’s easy to install, easy to use, and it’s written in Java, so it’s cross-platform. Another nice feature is the native support of CSV files, and the ability to quickly export the graph as an image file.
That said, there are a few things you should keep in mind when using it, which will make your life easier:
- When you are creating the format for your CSV file, put the time axis as the first entry, and make it a single value field, such as minutes or seconds (LG cannot parse a colon-delimited “time” format, i.e. 12:34:56).
- By default, LiveGraph uses samples as it’s x-axis, and plots the first field in the CSV as regular data. This means when you first load the CSV file, you’ll see a straight diagonal line on your graph which may dominate the plot. You can turn this off by clicking the appropriate checkbox in the “data series settings” window.
- You can tell LG to use time (the first field in the CSV) as the x-axis by choosing “data series” at the bottom of the “graph settings” window. This is exceedingly helpful if you are not logging data at regular intervals, but rather whenever some event occurs.
- If you want to export your plot as an image, you can do that through the “LiveGraph” window in the “plot” menu. Something to remember though: even though you’ve chosen the image file type (jpg, png, etc.) you still have to manually add the extension to the file name (“myplot.png”).
*In case you are wondering, the plot above represents barometric data collected with the logger shield and a pressure sensor on the Protoshield. It’s recording the relative pressure change as I venture into New York City. Those two high peaks, representing higher pressure, are under the Hudson river.