I have a linear regression where the output variable is always greater equal zero with a nontrivial weight at exactly zero. The predictions of the model are also always greater than zero. What should a good residual plot look like?
The plot shows my actual residuals, plotted with R. There are roughly 10 million data points, so it shows densities. The plot is cut off to residuals smaller than 7. Most of the output variable are between 0 and 3, so there is a lot more density there but the output variable has a roughly exponential drop off with about a dozen data points bigger than 100.
As both output variable and prediction are postive there are no residuals in the triangle in the bottom left corner. What is the expected residual distribution in this setting?