Recalibrating axis of graph automatically generated by Matlab

I used the PSD function(Eg: psd ECG) to generate the PSD of an ECG signal. The x axis was the normalized frequency and the y-axis the amplitude in dB.

I want to recalibrate the axis so that it shows the frequency in Hertz and the amplitude in mV. How can I do this? If I had written my own PSD fuction then while plotting I could have calibrated the axis according to my requirements.

The problem here is that I am using a pre-defined function to calculate the PSD. So, matlab automatically generates the graph to show freq in a normalized form.

I want to be able to edit the figure so I have the frequency in Hertz. How do i do it.?

[Walter Roberson]

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Answer 1

[Walter Roberson]

fs = 8000;  %sampling frequency

for H = findobj(gca, '-property', 'xdata')
  set(h, 'XData', get(H, 'XData') * (2*fs));
end

I do not happen to recall the conversion between dB and mV, but once you know that you can use code similar to the above.