fminstop: an OutputFcn / PlotFcns function which displays a 'STOP' button this later can be pressed during a fit to abort the current fit procedure. Other defined function to be used as OutputFcn and PlotFcns: @fminplot shows criteria and parameter space, with a STOP button @optimplotx plots the current point @optimplotfval plots the function value @optimplotfunccount plots the function count example: fmin(@objective, [], 'OutputFcn=fminplot')