Remove mean from numpy matrix

Question

I have a numpy matrix A where the data is organised column-vector-vise i.e A[:,0] is the first data vector, A[:,1] is the second and so on

Answer 1

Yes. pylab.demean:

In [1]: X = scipy.rand(2,3)

In [2]: X.mean(axis=1)
Out[2]: array([ 0.42654669,  0.65216704])

In [3]: Y = pylab.demean(X, axis=1)

In [4]: Y.mean(axis=1)
Out[4]: array([  1.85037171e-17,   0.00000000e+00])

Source:

In [5]: pylab.demean??
Type:           function
Base Class:     
String Form:    
Namespace:      Interactive
File:           /usr/lib/pymodules/python2.7/matplotlib/mlab.py
Definition:     pylab.demean(x, axis=0)
Source:
def demean(x, axis=0):
    "Return x minus its mean along the specified axis"
    x = np.asarray(x)
    if axis == 0 or axis is None or x.ndim <= 1:
        return x - x.mean(axis)
    ind = [slice(None)] * x.ndim
    ind[axis] = np.newaxis
    return x - x.mean(axis)[ind]