Incorrect equation

[Ryan-Bringenberg]

The current formula used is a simplification of
formula: min + (max - min)/(1 + (x/ic50)^hill
where the minimum response is 0. However, according to this mathworks (see link below), the hill coefficient should be negative.

https://www.mathworks.com/matlabcentral/fileexchange/38124-three-parameters-logistic-regression-there-and-back-again#:~:text=The%25203PL%2520equation%2520is%253A%2520F%2520%2528x%2529%2520%253D%2520D%252F,curve.%2520It%2520could%2520either%2520be%2520positive%2520or%2520negative.

[iansind]

The Hill coefficient directionality depends on whether inhibition or promotion is occuring. This will be added when objects are implemented.