[SciPy-user] odrpack changing the shape of a matrix

James Phillips zunzun@zunzun....
Mon May 19 17:12:03 CDT 2008


The example code below demonstrates odrpack changing the shape of a matrix.

I code around this behavior with a dummy 'second list' as shown below.

     James Phillips
     http://zunzun.com


import numpy,  scipy.odr.odrpack

def f(B, x):

    if len(x.shape) == 2:
        print 'x.shape OK:',  x.shape
    else:
        print 'x.shape ** changed **  --> ',  x.shape

    return B[0] + x[0]*B[1]  + x[0]*x[0]*x[0]*B[2]   # constant + ax + bx^3


good_X_data = numpy.array([[1.0, 2.0, 3.0, 4.0, 5.0], [0, 0, 0, 0, 0]])  #
second list is only needed for illustration
bad_X_data = numpy.array([[1.0, 2.0, 3.0, 4.0, 5.0]])  # no second list, the
function f() above shows shape change

ydata = numpy.array([1.0, 2.0, 2.0, 2.0, 3.0])
coefficients = numpy.array([0.89655172413793, 0.33646812957158,
0.00208986415883])
model = scipy.odr.odrpack.Model(f)

goodRealData = scipy.odr.odrpack.RealData(good_X_data, ydata)
badRealData = scipy.odr.odrpack.RealData(bad_X_data, ydata)

# independant data (X) unchanged
myodr = scipy.odr.odrpack.ODR(goodRealData, model, beta0=coefficients,
maxit=0)
myodr.set_job(var_calc=0)
myoutput = myodr.run()
print 'Good Std Error:', myoutput.sd_beta,  '  (should be [ 0.81412536
0.45377835  0.0142225 ])'

# independant data (X) changes shape
myodr = scipy.odr.odrpack.ODR(badRealData, model, beta0=coefficients,
maxit=0)
myodr.set_job(var_calc=0)
myoutput = myodr.run()
print 'Bad Std Error:', myoutput.sd_beta,  '  (should be [ 0.81412536
0.45377835  0.0142225 ])'
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