Figure 3
From: Modeling survival in colon cancer: a methodological review

Schoenfeld Residual Plot for β Trt2 . Schoenfeld residual plot for βTrt2. The black solid line is Trt2, a smooth function fit to the residuals, and the dotted line shows the actual dependence of βTrt2 on t (which is known in this case because the data have been simulated).