title: Gnuplot: Undifined value during function evaluation
body: <p>i need to fit some data with sum of exponantial functions, but this shows all the time. Any suggestions how to do the fit?<a href="https://i.stack.imgur.com/sq5iW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sq5iW.png" alt="this is what it says after trying to fit the data"></a></p>
  
  <p><a href="https://i.stack.imgur.com/AbfAA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AbfAA.png" alt="This is my datafile"></a></p>