Request user input and using that ans for my functions?

How can I use the user's input and convert it to a numerical value to be used in my remaining codes?

prompt=('Enter a threshold value to convert the grayscale image to black and white: ');
dlg_title=('Threshold level value');
num_lines=1;
defaultans={'0.5'};
answer=inputdlg(prompt,dlg_title,num_lines,defaultans);

Answer 1

[Stephen23]

>> val = str2double(answer{1})
val =
     3