Measured realized gain pattern values

I have a measured data and I have been told that it is realized gain pattern values. Does that mean that these values are output from measurement instrument after some internal calibration.? And if so how can calculate the directivity from it, given that I have no information of input power and any other loss factors.?

You can do a relative directivity, where all the gain points are related to a maximum gain point.
For example if you get an antenna gain pattern from 0 deg to 360 deg (step by 15 deg), and you get a maximum antenna gain at 30 deg, consider that gain point 0dB.
Relate (in dB) all the other point measurements to this 0dB point, and finally you get the relative directivity of your antenna, where you don't have to know input power or losses.

@vfone this seems to be on way. But in order to do that first of all I need to calculate/find maximum gain value. I have complex values in spherical coordinates ( Etheta and Ephi) how can calculate maximum gain from these values given that these are realized gain pattern values.

After some investigation I thought of one way that if the values are realized gain values then just searching maximum value from combined value i.e. (sqrt(Etheta^2+Ephi^2)) can give me maximum gain value. Is it a right way.? Because normally you cannot calculate gain value directly from field values.

You can reference your measured data from Antenna Under Test with reference dipole. Just make sure the feeds are the same, feed does not screw dipoles' pattern and match is perfect. Then dipole Gain at boresight is ~2 dBi.