Computes the Gaussian function in 1D:
x = Co-ordinate
x0 = Centre of function
FWHM = Full Width Half Max of the function
order = Gaussian order
Normal Gaussian is of order 1.
Note that FWHM = (1/e Half Width)/sqrt(2*log(2))
log is the natural log.
Adam Wyatt (2020). Integer order 1D Gaussian function (https://www.mathworks.com/matlabcentral/fileexchange/15635-integer-order-1d-gaussian-function), MATLAB Central File Exchange. Retrieved .