I prefer inputdlg, however you need to remembert that the output is a cell array or character vectors.
To enter an amplitude value of 42:
ac = inputdlg('Enter a value for the amplitude ')
a = str2double(ac)
produces:
ac =
1×1 cell array
{'42'}
a =
42
Put semiccolons at the end of the statements to prevent them printing to your Command Window. I did not use them here for demonstration purposes.
