Is it possible to build non-linear resistor using linear potentiometer
If you examine the table you can see a reasonably linear relationship between resistor current and LED current. This is implied in the data sheet where it says that LED current is 400 times Rset current. So, given that Vset is constant at 1.2 volts, for an Rset of 4990 ohms, Iset will be 0.24mA and Iled will be 400 x higher at 96mA (not far off 100mA). At mid scale (say) 1050 ohms, Iset will be 1.143mA and Iled should be 457mA - it says 500mA in the table so it's not far off. At max LED current (1A) Iset is 2.185 mA and the LED current would probably be 400x higher at 874mA.

What I'm saying is that you could use an op-amp and a transistor to extract a controlled current from the Rset pin and you would find this to be significantly more linear than trying to delinearize a resistor: -



Iload in the diagram would connect to the Rset pin of the chip. Rset in the diagram above would ideally be slightly lower than 549 ohms - maybe a 470R would be fine. Vset in the diagram would force a current to flow into the collector that is Vset/470R and, for 400mA LED current would be approximately 0.47 volts.

Remember that the CAT4101 uses current mirrors to produce the overall target LED current and therefore feeding in a variable constant current is going to be more accurate that choosing a value for Rset no matter how delinearized.