I am fitting a linear model with one dependent variable and 5 independent variables. All variables are continuous. The residual plot (plot of residuals vs. predicted values) appears to have a decreasing trend. See the plot attached. Someone told me this means a non-linear relationship between the DV and the IVs. But I thought only a when a curvilinear relationship between the predicted values and the residuals implies a non-linear relationship between the DV and the IVs.
Anyway, can someone tell me if the residual plot indicates any violation of the assumptions of the linear regression (independence, linearity, normality, and homogeneous variance)? And, it does, how to fix the problems? Thanks.