CODEWITHSUNDEEP
pythonpython-2.7scipyregression
xpt
xpt

Reputation: 22994

Data fitting using fmin from scipy.optimize under jupyter notebook

I'm trying

Data fitting using fmin
http://glowingpython.blogspot.ca/2011/05/curve-fitting-using-fmin.html

Which contains the following code to use fmin:

# fitting the data with fmin
p0 = rand(3) # initial parameter value
p = fmin(e, p0, args=(x,y))

However, it is giving me the following error when I try it:

TypeErrorTraceback (most recent call last)
<ipython-input-1-41b53befd463> in <module>()
     22 # fitting the data with fmin
     23 p0 = rand(3) # initial parameter value
---> 24 p = fmin(e, p0, args=(x,y))
     25 
     26 print 'estimater parameters: ', p

TypeError: 'args' is an invalid keyword to ufunc 'fmin'

When I looked at doc here, I do see the args is a valid keyword.

UPDATE:

I was running the script as-is in Python2.7, and got the above error. Having seen Warren Weckesser's answer here is the updated script:

from pylab import *
import numpy as np
from numpy.random import normal
from scipy.optimize import fmin

%pylab inline

# parametric function, x is the independent variable
# and c are the parameters.
# it's a polynomial of degree 2
fp = lambda c, x: c[0]+c[1]*x+c[2]*x*x
real_p = rand(3)

# error function to minimize
e = lambda p, x, y: (abs((fp(p,x)-y))).sum()

# generating data with noise
n = 30
x = linspace(0,1,n)
y = fp(real_p,x) + normal(0,0.05,n)

# fitting the data with fmin
p0 = rand(3) # initial parameter value
p = fmin(e, p0, args=(x,y))

print 'estimater parameters: ', p
print 'real parameters: ', real_p

xx = linspace(0,1,n*3)
plot(x,y,'bo', xx,fp(real_p,xx),'g', xx, fp(p,xx),'r')

show()

and I'm still getting the exact same error as above.

How to fix it? Thx.

Upvotes: 1

Views: 906

Answers (1)

Warren Weckesser
Warren Weckesser

Reputation: 114811

It would be easier to help you if you provided a minimal, complete and verifiable example that reproduced the problem. Without that, we have to guess.

In this case, my guess is that you are actually using numpy.fmin, not scipy.optimize.fmin. Add the line

from scipy.optimize import fmin

at the top of your script. And if you are doing something like

from numpy import *

(as the code at glowingpython does), then remove that line, and either use

import numpy as np

and use the np. prefix with all the numpy names that you use, or explicitly import only those names from numpy that you actually use, e.g.

from numpy import array, linspace  # whatever you actually use
from numpy.random import rand      # etc.

Using the * form of import is a bad practice in scripts, for exactly the reason that you have this question.

It is true, however, that something like from pylab import * is very convenient when you are working interactively in ipython or in a jupyter notebook. To avoid the problem of fmin being shadowed by the fmin from numpy, you could do:

from scipy import optimize

and then call fmin using

p = optimize.fmin(e, p0, args=(x, y))

Upvotes: 1

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