I have a vector of deviance residuals, r, a vector of fitted values, yhat and I need to solve for a vector of actuals, y. The deviance residual formula is r={2(c ln c - c + 1)}^1/2. c=y/yhat. Since this can't be solved in closed form, I believe that I should be able to solve this numerically using a function like optim but I can't get my head around how to setup the problem and looking at the examples for optim it hasn't clicked for me. Any help would be appreciated. I am using this result as part of a funtion to do non-parametric bootstrapping of a glm to build a range around my parameter errors. Thanks. Bill -- View this message in context: http://www.nabble.com/Invert-Deviance-Residuals-tp23223703p23223703.html Sent from the R help mailing list archive at Nabble.com.