- tanh (x).
,
tanh(x) = sinh(x) / cosh(x) =
= [(1/2) (e^x - e^-x)] / [(1/2) (e^x + e^-x)] =
= (e^x - e^-x) / (e^x + e^-x) =
= (e^(2x) - 1) / (e^(2x) + 1)

( )
, . tanh , :
y = 1 + (e^(2x - 6) - 1) / (e^(2x - 6) + 1)

( )
JavaScript
exp2x = Math.exp(2*x)
y = (exp2x - 1) / (exp2x + 1)
()
, , y 0 100, x - 0 100,
y = 50 + 50*tanh((xβ50)/10)

( )
y = 50 + 50 * tanh((xβ50)/10)
= 50 + 50 * (e^((xβ50)/5) - 1) / (e^((xβ50)/5) + 1)
erf , ( JavaScript erf).
(OP) : !
var y = 50 + 50 * tanh((n-50)/10);
function tanh (arg) {
return (Math.exp(arg) - Math.exp(-arg)) / (Math.exp(arg) + Math.exp(-arg));
}