Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Rich Shepard
On Fri, 2 May 2008, Christopher Barker wrote: > Why not just scale to -pi to pi right there? Dunno, Chris. As I wrote to Anne (including a couple of files and the resulting plot), it's been almost three decades since I dealt with the math underlying distribution functions. > Which is why you

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Christopher Barker
Anne Archibald wrote: > 2008/5/2 Rich Shepard <[EMAIL PROTECTED]>: > No, no. You *want* scaled_x to range from -1 to 1. Why not just scale to -pi to pi right there? (The 0.998 is because you didn't include the endpoint, 100.) Which is why you want linspace, rather than arange. Really, trust me

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Anne Archibald
2008/5/2 Rich Shepard <[EMAIL PROTECTED]>: > On Fri, 2 May 2008, Anne Archibald wrote: > > > It's better not to work point-by-point, appending things, when working > > with numpy. Ideally you could find a formula which just produced the right > > curve, and then you'd apply it to the input vecto

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Rich Shepard
On Fri, 2 May 2008, Anne Archibald wrote: > It's better not to work point-by-point, appending things, when working > with numpy. Ideally you could find a formula which just produced the right > curve, and then you'd apply it to the input vector and get the output > vector all at once. Anne, T

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Anne Archibald
2008/5/2 Rich Shepard <[EMAIL PROTECTED]>: >What will work (I call it a pi curve) is a matched pair of sigmoid curves, > the ascending curve on the left and the descending curve on the right. Using > the Boltzmann function for these I can calculate and plot each individually, > but I'm havi

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread 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

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Christopher Barker
Rich, 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! Sp

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Rich Shepard
On Fri, 2 May 2008, Angus McMorland wrote: > How about multiplying two Boltzmann terms together, ala: > > f(x) = 1/(1+exp(-(x-flex1)/tau1)) * 1/(1+exp((x-flex2)/tau2)) > You'll find if your two flexion points get too close together, the peak > will drop below the maximum for each individual curve

Re: [Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Angus McMorland
2008/5/2 Rich Shepard <[EMAIL PROTECTED]>: >When I last visited I was given excellent advice about Gaussian and other > bell-shaped curves. Upon further reflection I realized that the Gaussian > curves will not do; the curve does need to have y=0.0 at each end. > >I tried to apply a Beta

[Numpy-discussion] Combining Sigmoid Curves

2008-05-02 Thread Rich Shepard
When I last visited I was given excellent advice about Gaussian and other bell-shaped curves. Upon further reflection I realized that the Gaussian curves will not do; the curve does need to have y=0.0 at each end. I tried to apply a Beta distribution, but I cannot correlate the alpha and bet