how to plot real-time fft of a signal acquired from arduino in matlab ?

hello guys, i am a newbie in matlab signal processing and also dont know exactly where to post this question, as in, in which forum. please pardon me

i am preparing for my final year project.I have acquired a signal through arduino in matlab using matlab-arduino interface.

everything is working fine. but, when i try to take the fft of that signal in real time, an error pops out in the matlab command window : "Index extends matrix dimensions". and i am not able to find the error exactly and my project has come to a stand still. i have attached an image of my script...

i just want to get the peak amplitude of that signal...so please correct me if i have written the wrong script... it would be great if someone helps me to come out from this situation.

Thank you in advance.

[Geoff Hayes]

Rgv - it would be easier to just attach the code rather than an image of it. As well, you must have an idea of where the error is occurring. Can you copy and paste the complete error message (all of the red text) to your question?

The error message is telling you that you are trying to extract more data than exists from an array. An example would be

 X = zeros(42,1);
 X(1:100)

which generates the

 Index exceeds matrix dimensions.

error. Something similar in your code could be the

 d(1:500)

Are you sure that d, the input signal acquired from Arduino, has at least 500 elements?

[Geoff Hayes]

Ella's answer moved here

Can you please share the solution with us ?