How to capture time interval between two keypress.

I want to capture time between two keypress .Time when one key is released and next key is pressed.I made code using cputime.Its like

function Keyrelease_Test

h = figure;

set(h,'KeyReleaseFcn',@KeyUpCb,'KeyPressFcn',@KeyDownCb)

StartTime=0;

function KeyUpCb(~,~)

    StartTime=cputime;

    end

    function KeyDownCb(~,~)

      Time=cputime-StartTime;

        disp(Time)
    end
end

but when i press 3 key it gives output like: >> Keyrelease_Test 54.8968

    0.1872

     0

    0.0156
but for 3 keypress it must give 2 time.please help me
i have also made code using now

function Keyrelease_Set

h = figure;

set(h,'KeyReleaseFcn',@KeyUpCb,'KeyPressFcn',@KeyDownCb)

t1=0;

t2=0;

function KeyUpCb(~,~)

    t1=rem(now,1);

end

    function KeyDownCb(~,~)
        t2=rem(now,2);

     Time=t2-t1;

      disp(Time)
        end

   end
 for 2 keypress it gives output like
 Keyrelease_Set
    0.8938

   1.6852e-05 
please help me with this code or i have to use any other function or logic??

Answer 1

[Geoff Hayes]

In your first function, you are using the cputime command which, according to the documentation - type help cputime in the command window, returns the CPU time in seconds that has been used by the MATLAB process since MATLAB started. So this is not an appropriate function to use when measuring the difference between key presses and release.

In your second function, you are using the now command which, according to the documentation - type help now in the command window, returns the current date and time as a serial date number. So the values you are seeing are reasonable though are not in the expected seconds. Your use of rem(t1,1) returns the current time (though in the KeyDownCb you are using t2=rem(now,2) so you may wish to change the 2 to a 1). If you want to convert this to seconds, then you should apply the following conversion

 function KeyDownCb(~,~)
     DAYS_TO_SECS = 24*60*60;
     t2=rem(now,1);
     timeSecs=(t2-t1)*DAYS_TO_SECS;
     disp(timeSecs)
 end

The above conversion is used since the serial date number is a single number equal to the number of days since January 0, 0000 (see http://www.mathworks.com/help/matlab/matlab_prog/represent-date-and-times-in-MATLAB.html). Since you probably want seconds between key presses, then we just do the days to second conversion as 24 hours * 60 minutes * 60 seconds.

Try the above and see what happens.

[puja dutta]

thanks for your help.i got my answer actually i am using wrong logic.thanks alot