Hello OOI JUN HANG,
From what I gather, you're having trouble in achieving outputs in the interval of [-1, 1] with the tansig function. The 'tansig' activation function is designed to yield results that always fall between -1 and 1, irrespective of the architecture it's applied to. Formula for tansig is,
tansig(x) = 2/(1+exp(-2*x)) – 1 = (1 – exp(-2*x))/(1+exp(-2*x)) ---- (2)
now if you just take the reciprocal of exp(-2*x) in both numerator and denominator we get,
tansig(x) = (exp(2*x)-1) / (exp(2*x) +1) ---- (3)
Now when x tends to infinity tansig(x) tends to 1 as exp(-2*x) becomes zero and we are left with (1/1) (see equation 2).
When x tends to -1*infinity tansig(x) tends to -1 as exp(2*x) becomes zero and we are left with (-1/1) (see equation 3).
This is why the range for tansig is [-1,1]. For more information, please go through this documentation,
Hope this helps.
