Below is a very simple circuit to extract the transconductance value of the MOSFET.

As it is known, transconductance is known as Delta (Id) / Delta (Vgate).

For the gate voltage, I defined it as .step param X 0 12 0.5.

What I want to do, for example, is the amount of change from 0V to 0.5V, 0.5V - 0V = 0.5V or 1V - 0.5 up to 12 V. I want to do the same for Id corresponding to the amount of change and find their ratio.                                                                                                             

Should I continue for every value like below:  
.meas TRAN Vg FIND V(out) WHEN V(X)=0.5   
.meas TRAN Vg FIND V(out) WHEN V(X)=1   
.meas TRAN Vg FIND V(out) WHEN V(X)=1.5
.
.
.

doing the same for Id and using .meas DELTA param makes the process too long.

Maybe I am wrong but is there any other correct way to do it?

[![enter image description here][1]][1]


[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/kZ8z0oyb.png
  [2]: https://i.sstatic.net/M1VkbOpB.png
Source: https://www.mouser.com.tr/datasheet/2/240/media-3322045.pdf