So, I am trying to perform a global fit on 15 data traces obtained from electrophysiology. The first three traces had a concentration of 10 micromolar, the second three traces had a concentration of 100 micromolar, the third three traces had 500 micromolar, the fourth had 1 millimolar, and the fifth had 10 millimolar. The traces are nanoamps vs milliseconds. Ok, so I want to globally fit these 15 traces using a nonlinear custom nonlinear function with lsqcurvefit. Fitting the first three traces was simple since they all had the same concentration. How would I fit all of these traces using my nonlinear function and lsqcurvefit in a loop where the concentration changes? I thought maybe putting all of the xdata (milliseconds) in one matrix, and the ydata (nanoamps) in another matrix and using those as the xdata and ydata that are called into lsqcurvefit, and that worked if the concentration is a fixed number. Now, how would I do this if my matrix was 15 dimensions, and every three columns I needed the nonlinear function to start using a different concentration? I hope this was mostly clear.