To find index of maximum value

I am taking the FFT of match filter output. In graph it is showing correct frequency but whem I am using max() function to find the index of maximum value, I am getting wrong value that is 30051. How can I remove this error please help? The fft plot is shown in figure.

[Rik]

The max function will return the index, not the value. If you want to get the corresponding frequency you'll have to put that index in your frequency vector.

[Harish Kumawat]

can you please tell how to do it?

[Harish Kumawat]

Thanks I got it