[Numpy-discussion] Combining Sigmoid Curves

[Rich Shepard]

On Fri, 2 May 2008, Christopher Barker wrote:

> this could use some serious vectorization/numpyification! Poke around the
> scipy Wiki and whatever other tutorials you can find -- you'll be glad you
> did. A hint:
>
> When you are writing a loop like:
>>  	  for i in xL:
>>  	    x.append(xL[i])
>
> You should be doing array operations!

Chris,

   Good suggestions. I need to append the two numpy arrays so I return all x
values in a single list and all y values in another list. I'll read the
numpy book again.

> That's why you get this error:
> TypeError: unsupported operand type(s) for -: 'list' and 'float'
>
> you're trying to do array operations on a list.

   Ah, so!

> Also, you probably want np.linspace, rather than arange, it's a better
> option for floats.

   arange() has worked just fine in other functions.

> # now put them together:
> x = np.hstack((xL, xR[1:])) # don't want to duplicate the midpoint
> y = np.hstack((yL, yR[1:]))

> Also, you don't need to create the separate left and right arraysand put
> them together, slicing gives a view, so you could do:

   I assume that there's a way to mate the two curves in a single equation.
I've not been able to find what that is.

Thanks,

Rich