Hello all, I am using matplotlib for a web application to
> create trend charts from measurements stored in a database.
> Specifically I use plot_date to plot the values vs their
> timestamps. Occasionally and without any obvious to me
> reason, plot_date raises the exception
> "ordinal must be >= 1"
> I check that both the x and y value sequences are not empty
> and their length is certainly above 1. Does anybody know
> where this "ordinal" refers to and what might be causing
> this error? Thank you very much
I sometimes see this when a date graph is open in a GUI window and I
am moving my mouse. The mouse as is passes off the axes can return
invalid dates to the matplotlib date conversion routine. I think I
added some guards against this in the last release (0.86.2). What
version are you using.
In a nutshell, it likely means that somewhere in the pipeline
matplotlib is getting an illegal date value.
Next time you get the error, lease post version info and a complete
traceback.
JDH