Everything seems to work, but I feel like this is a poor code. Is there a better way to do this? (say only plot the function once, and for each slider only vary one parameter?)
How are you plotting the data?
I would recommend taking the "plot once modify later" approach. To do this, save the handle ( setappdata and the handles structure (or get the children of the axes)) to the plotted object (line, image, surface, - whatever it is) and maybe the axes, and update it's properties based on the new values. This could mean getting the 'xdata', or 'ydata', or 'linewidth, updating it and setting it. Since this probably isn't clear at all, here's pseudoish code for a slider callback:
function slidercallback(hObject,eventdata,handles);
hLine = get(handles.axes1,'children'); %get handle to children of axes1
%let's assume it's one line for this example
set(hLine,'linewidth',get(hObject,'value')); %set line width to slider value
