I'm trying to find a full example of how to plot learning curves.
I watched Andrew Ng's ML class on Coursera and he mentions using learning curves to diagnose variance-bias issues.
My notes show the top line as the test set or cv error slopping downward as the number of training examples increases. This makes sense to me.
My problem is on the lower line of the plot which is training error. I'm not sure what this means and why the error would increase with more training examples. Should the training error be multiplied by -1? Or is there something else I need to do?
Any working examples would be appreciated as would an R package that helps with this.