示例#1
0
def SVD(var1,
        var2,
        num=1,
        subspace=-1,
        iaxis=Time,
        weight1=True,
        weight2=True,
        matrix='cov'):
    """
  Finds coupled EOFs of two fields.  Note that the mean/trend/etc. is NOT
  removed in this routine.

  Parameters
  ----------
  var1, var2 : :class:`Var`
    The variables to analyse.

  num : integer
    The number of EOFs to compute (default is ``1``).

  weight1, weight2 : optional 
    Weights to use for defining orthogonality in the var1, var2 domains,
    respectively.  Patterns X and Y in the var1 domain are orthogonal if the
    sum over X*Y*weights1 is 0. Patterns Z and W in the var2 domain are
    orthogonal if the sum over Z*W*weights2 is 0. Default is to use internal
    weights defined for var1 accessed by :meth:`Var.getweights()`. If set to
    ``False`` no weighting is used.

  matrix : string, optional ['cov']
    Which matrix we are diagonalizing (default is 'cov'). 
     * 'cov': covariance matrix of var1 & var2
     * 'cov': correlation matrix of var1 & var2

  iaxis : Axis identifier
    The principal component / expansion coefficient axis, i.e., the 'time'
    axis. Can be an integer (the axis number, leftmost = 0), the axis name
    (string), or a Pygeode axis class.  If not specified, will try to use
    pygeode.timeaxis.Time, and if that fails, the leftmost axis.

  Returns
  -------
  (eof1, pc1, eof2, pc2): tuple
    * eof1: The coupled eof patterns for var1. 
    * pc1: The principal component / expansion coefficients for var1.
    * eof2: The coupled eof patterns for var2.
    * pc2: The principal component / expansion coefficients for var2.

  Notes
  -----
    Multiple orders of EOFs are concatenated along an 'order' axis.
  """
    import numpy as np
    from pygeode.timeaxis import Time
    from pygeode.var import Var
    from pygeode.view import View
    from pygeode import MAX_ARRAY_SIZE
    from warnings import warn
    from pygeode import svdcore as lib

    if matrix in ('cov', 'covariance'): matrix = 'cov'
    elif matrix in ('cor', 'corr', 'correlation'): matrix = 'cor'
    else:
        warn("invalid matrix type '%'.  Defaulting to covariance." % matrix,
             stacklevel=2)
        matrix = 'cov'

    MAX_ITER = 1000

    # Iterate over more EOFs than we need
    # (this helps with convergence)
    # TODO: a more rigorous formula for the optimum number of EOFs to use
    if subspace <= 0: subspace = 2 * num + 8
    if subspace < num: subspace = num  # Just in case

    # Remember the names
    prefix1 = var1.name + '_' if var1.name != '' else ''
    prefix2 = var2.name + '_' if var2.name != '' else ''

    # Apply weights?
    #  if weight1 is not None: var1 *= weight1.sqrt()
    #  if weight2 is not None: var2 *= weight2.sqrt()
    if weight1 is True: weight1 = var1.getweights()
    if weight1 is not False:
        assert not weight1.hasaxis(
            iaxis), "Can't handle weights along the record axis"
        # Normalize the weights
        W = weight1.sum() / weight1.size
        weight1 /= W
        # Apply the weights
        var1 *= weight1.sqrt()
    if weight2 is True: weight2 = var2.getweights()
    if weight2 is not False:
        assert not weight2.hasaxis(
            iaxis), "Can't handle weights along the record axis"
        # Normalize the weights
        W = weight2.sum() / weight2.size
        weight2 /= W
        # Apply the weights
        var2 *= weight2.sqrt()

    #TODO: allow multiple iteration axes (i.e., time and ensemble)
#  if iaxis is None:
#    if var1.hasaxis(Time) and var2.hasaxis(Time):
#      iaxis1 = var1.whichaxis(Time)
#      iaxis2 = var2.whichaxis(Time)
#    else:
#      iaxis1 = 0
#      iaxis2 = 0
#  else:
    iaxis1 = var1.whichaxis(iaxis)
    iaxis2 = var2.whichaxis(iaxis)

    assert var1.axes[iaxis1] == var2.axes[
        iaxis2], "incompatible iteration axes"
    del iaxis  # so we don't use this by accident

    # Special case: can load entire variable in memory
    # This will save some time, especially if the field is stored on disk, or is heavily derived
    if var1.size <= MAX_ARRAY_SIZE:
        print('preloading ' + repr(var1))
        var1 = var1.load()
    if var2.size <= MAX_ARRAY_SIZE:
        print('preloading ' + repr(var2))
        var2 = var2.load()

    # Use correlation instead of covariance?
    # (normalize by standard deviation)
    if matrix == 'cor':
        print('computing standard deviations')
        std1 = var1.stdev(iaxis1).load()
        std2 = var2.stdev(iaxis2).load()
        # account for grid points with zero standard deviation?
        std1.values = std1.values + (std1.values == 0)
        std2.values = std2.values + (std2.values == 0)
        var1 /= std1
        var2 /= std2

    eofshape1 = (subspace, ) + var1.shape[:iaxis1] + var1.shape[iaxis1 + 1:]
    eofshape2 = (subspace, ) + var2.shape[:iaxis2] + var2.shape[iaxis2 + 1:]

    pcshape1 = (var1.shape[iaxis1], subspace)
    pcshape2 = (var2.shape[iaxis2], subspace)

    # number of spatial grid points
    NX1 = var1.size // var1.shape[iaxis1]
    assert NX1 <= MAX_ARRAY_SIZE, 'field is too large!'
    NX2 = var2.size // var2.shape[iaxis2]
    assert NX2 <= MAX_ARRAY_SIZE, 'field is too large!'

    # Total number of timesteps
    NT = var1.shape[iaxis1]
    # Number of timesteps we can do in one fetch
    dt = MAX_ARRAY_SIZE // max(NX1, NX2)

    pcs1 = np.empty(pcshape1, dtype='d')
    pcs2 = np.empty(pcshape2, dtype='d')

    X = np.empty(eofshape2, dtype='d')
    U = np.empty(eofshape1, dtype='d')
    # Seed with sinusoids superimposed on random values
    Y = np.random.rand(*eofshape1)
    V = np.random.rand(*eofshape2)
    from math import pi
    for i in range(subspace):
        Y[i, ...].reshape(NX1)[:] += np.cos(
            np.arange(NX1, dtype='d') / NX1 * 2 * pi * (i + 1))
        V[i, ...].reshape(NX2)[:] += np.cos(
            np.arange(NX2, dtype='d') / NX2 * 2 * pi * (i + 1))


#  raise Exception

# Workspace for C code
    UtAX = np.empty([subspace, subspace], dtype='d')
    XtAtU = np.empty([subspace, subspace], dtype='d')
    VtV = np.empty([subspace, subspace], dtype='d')
    YtY = np.empty([subspace, subspace], dtype='d')

    # Views over whole variables
    # (rearranged to be compatible with our output eof arrays)
    view1 = View((var1.axes[iaxis1], ) + var1.axes[:iaxis1] +
                 var1.axes[iaxis1 + 1:])
    view2 = View((var2.axes[iaxis2], ) + var2.axes[:iaxis2] +
                 var2.axes[iaxis2 + 1:])

    for iter_num in range(1, MAX_ITER + 1):

        print('iter_num: %d' % iter_num)

        assert Y.shape == U.shape
        assert X.shape == V.shape
        U, Y = Y, U
        X, V = V, X

        # Reset the accumulation arrays for the next approximations
        Y[()] = 0
        V[()] = 0

        # Apply the covariance/correlation matrix
        for t in range(0, NT, dt):
            # number of timesteps we actually have
            nt = min(dt, NT - t)

            # Read the data
            chunk1 = view1.modify_slice(0, slice(t, t + nt)).get(var1)
            chunk1 = np.ascontiguousarray(chunk1, dtype='d')
            chunk2 = view2.modify_slice(0, slice(t, t + nt)).get(var2)
            chunk2 = np.ascontiguousarray(chunk2, dtype='d')

            ier = lib.build_svds(subspace, nt, NX1, NX2, chunk1, chunk2, X, Y,
                                 pcs2[t, ...])
            assert ier == 0
            ier = lib.build_svds(subspace, nt, NX2, NX1, chunk2, chunk1, U, V,
                                 pcs1[t, ...])
            assert ier == 0

        # Useful dot products
        lib.dot(subspace, NX1, U, Y, UtAX)
        lib.dot(subspace, NX2, V, V, VtV)
        lib.dot(subspace, NX1, Y, U, XtAtU)
        lib.dot(subspace, NX1, Y, Y, YtY)

        # Compute surrogate matrices (using all available information from this iteration)
        A1, residues, rank, s = np.linalg.lstsq(UtAX, VtV, rcond=1e-30)
        A2, residues, rank, s = np.linalg.lstsq(XtAtU, YtY, rcond=1e-30)

        # Eigendecomposition on surrogate matrices
        Dy, Qy = np.linalg.eig(np.dot(A1, A2))
        Dv, Qv = np.linalg.eig(np.dot(A2, A1))

        # Sort by eigenvalue (largest first)
        S = np.argsort(np.real(Dy))[::-1]
        Dy = Dy[S]
        Qy = np.ascontiguousarray(Qy[:, S], dtype='d')
        S = np.argsort(np.real(Dv))[::-1]
        Dv = Dv[S]
        Qv = np.ascontiguousarray(Qv[:, S], dtype='d')

        # get estimate of true eigenvalues
        D = np.sqrt(Dy)  # should also = np.sqrt(Dv) in theory
        print(D)

        # Translate the surrogate eigenvectors to an estimate of the true eigenvectors
        lib.transform(subspace, NX1, Qy, Y)
        lib.transform(subspace, NX2, Qv, V)

        # Normalize
        lib.normalize(subspace, NX1, Y)
        lib.normalize(subspace, NX2, V)

        if not np.allclose(U[:num, ...], Y[:num, ...], atol=0): continue
        if not np.allclose(X[:num, ...], V[:num, ...], atol=0): continue
        print('converged after %d iterations' % iter_num)
        break

    assert iter_num != MAX_ITER, "no convergence"

    # Flip the sign of the var2 EOFs and PCs so that the covariance is positive
    lib.fixcov(subspace, NT, NX2, pcs1, pcs2, V)

    # Wrap as pygeode vars, and return
    # Only need some of the eofs for output (the rest might not have even converged yet)
    orderaxis = order(num)

    eof1 = np.array(Y[:num])
    pc1 = np.array(pcs1[..., :num]).transpose()
    eof1 = Var((orderaxis, ) + var1.axes[:iaxis1] + var1.axes[iaxis1 + 1:],
               values=eof1)
    pc1 = Var((orderaxis, var1.axes[iaxis1]), values=pc1)

    eof2 = np.array(V[:num])
    pc2 = np.array(pcs2[..., :num]).transpose()
    eof2 = Var((orderaxis, ) + var2.axes[:iaxis2] + var2.axes[iaxis2 + 1:],
               values=eof2)
    pc2 = Var((orderaxis, var2.axes[iaxis2]), values=pc2)

    # Apply weights?
    if weight1 is not False: eof1 /= weight1.sqrt()
    if weight2 is not False: eof2 /= weight2.sqrt()

    # Use correlation instead of covariance?
    # Re-scale the fields by standard deviation
    if matrix == 'cor':
        eof1 *= std1
        eof2 *= std2

    # Give it a name
    eof1.name = prefix1 + "EOF"
    pc1.name = prefix1 + "PC"
    eof2.name = prefix2 + "EOF"
    pc2.name = prefix2 + "PC"

    return eof1, pc1, eof2, pc2
示例#2
0
文件: eof.py 项目: aerler/pygeode
def EOF_iter (x, num=1, iaxis=None, subspace = -1, max_iter=1000, weight=True, out=None):
  """
  (See svd.SVD for documentation on a similar function, but replace each xxx1 and xxx2 parameter with a single xxx parameter.)
  """
  import numpy as np
  from pygeode import libpath
  from pygeode.view import View
  from math import sqrt
  from pygeode.varoperations import fill
  from pygeode import svdcore as lib

  # Iterate over more EOFs than we need
  # (this helps with convergence)
  # TODO: a more rigorous formula for the optimum number of EOFs to use
  if subspace <= 0: subspace = 2*num + 8
  if subspace < num: subspace = num

  # Run the single-pass guess to seed the first iteration
  guess_eof, guess_eig, guess_pc = EOF_guess (x, subspace, iaxis, weight=weight, out=None)
  # Convert NaNs to zeros so they don't screw up the matrix operations
  guess_eof = fill (guess_eof, 0)

  x, time, space = prep(var=x, iaxis=iaxis, weight=weight, out=out)
  del iaxis

  eofshape =  (subspace,) + space.shape
  pcshape =  time.shape + (subspace,)

  pcs = np.empty(pcshape,dtype='d')

  oldeofs = np.empty(eofshape,dtype='d')
  # Seed with initial guess (in the weighted space)
  neweofs = apply_weights (guess_eof, weight=weight).get()
  neweofs = np.array(neweofs, dtype='d')  # so we can write
#  neweofs = np.random.rand(*eofshape)

  # Workspace for smaller representative matrix
  work1 = np.empty([subspace,subspace], dtype='d')
  work2 = np.empty([subspace,subspace], dtype='d')

  NX = space.size

  # Variance accumulation (on first iteration only)
  variance = 0.0

  for iter_num in range(1,max_iter+1):

    print 'iter_num:', iter_num

    neweofs, oldeofs = oldeofs, neweofs

    # Reset the accumulation arrays for the next approximations
    neweofs[()] = 0

    # Apply the covariance matrix
    for inview in View(x.axes).loop_mem():
      X = np.ascontiguousarray(inview.get(x), dtype='d')
      assert X.size >= space.size, "spatial pattern is too large"

      nt = inview.shape[0]
      time_offset = inview.slices[0].start
      ier = lib.build_eofs (subspace, nt, NX, X, oldeofs,
                            neweofs, pcs[time_offset,...])
      assert ier == 0

      # Compute variance?
      if iter_num == 1:
        variance += (X**2).sum()

    # Useful dot products
    lib.dot(subspace, NX, oldeofs, neweofs, work1)
    lib.dot(subspace, NX, neweofs, neweofs, work2)

    # Compute surrogate matrix (using all available information from this iteration)
    A, residues, rank, s = np.linalg.lstsq(work1,work2,rcond=1e-30)

    # Eigendecomposition on surrogate matrix
    w, P = np.linalg.eig(A)

    # Sort by eigenvalue
    S = np.argsort(w)[::-1]
    w = w[S]
    print w
#    assert P.dtype.name == 'float64', P.dtype.name
    P = np.ascontiguousarray(P[:,S], dtype='d')

    # Translate the surrogate eigenvectors to an estimate of the true eigenvectors
    lib.transform(subspace, NX, P, neweofs)

    # Normalize
    lib.normalize (subspace, NX, neweofs)

#    # verify orthogonality
#    for i in range(num):
#      print [np.dot(neweofs[i,...].flatten(), neweofs[j,...].flatten()) for j in range(num)]

    if np.allclose(oldeofs[:num,...],neweofs[:num,...], atol=0):
      print 'converged after %d iterations'%iter_num
      break

  assert iter_num != max_iter, "no convergence"

  # Wrap as pygeode vars, and return
  # Only need some of the eofs for output (the rest might not have even converged yet)
  eof = neweofs[:num]
  pc = pcs[...,:num].transpose()

  # Extract the eigenvalues
  # (compute magnitude of pc arrays)
  #TODO: keep eigenvalues as a separate variable in the iteration loop
  eig = np.array([sqrt( (pc[i,...]**2).sum() ) for i in range(pc.shape[0]) ])
  pc = np.dot(np.diag(1/eig), pc)

  return finalize (x, time, space, eof, eig, pc, variance, weight=weight, out=out)
示例#3
0
文件: svd.py 项目: neishm/pygeode
def SVD (var1, var2, num=1, subspace=-1, iaxis=Time, weight1=True, weight2=True, matrix='cov'):
  """
  Finds coupled EOFs of two fields.  Note that the mean/trend/etc. is NOT
  removed in this routine.

  Parameters
  ----------
  var1, var2 : :class:`Var`
    The variables to analyse.

  num : integer
    The number of EOFs to compute (default is ``1``).

  weight1, weight2 : optional 
    Weights to use for defining orthogonality in the var1, var2 domains,
    respectively.  Patterns X and Y in the var1 domain are orthogonal if the
    sum over X*Y*weights1 is 0. Patterns Z and W in the var2 domain are
    orthogonal if the sum over Z*W*weights2 is 0. Default is to use internal
    weights defined for var1 accessed by :meth:`Var.getweights()`. If set to
    ``False`` no weighting is used.

  matrix : string, optional ['cov']
    Which matrix we are diagonalizing (default is 'cov'). 
     * 'cov': covariance matrix of var1 & var2
     * 'cov': correlation matrix of var1 & var2

  iaxis : Axis identifier
    The principal component / expansion coefficient axis, i.e., the 'time'
    axis. Can be an integer (the axis number, leftmost = 0), the axis name
    (string), or a Pygeode axis class.  If not specified, will try to use
    pygeode.timeaxis.Time, and if that fails, the leftmost axis.

  Returns
  -------
  (eof1, pc1, eof2, pc2): tuple
    * eof1: The coupled eof patterns for var1. 
    * pc1: The principal component / expansion coefficients for var1.
    * eof2: The coupled eof patterns for var2.
    * pc2: The principal component / expansion coefficients for var2.

  Notes
  -----
    Multiple orders of EOFs are concatenated along an 'order' axis.
  """
  import numpy as np
  from pygeode.timeaxis import Time
  from pygeode.var import Var
  from pygeode.view import View
  from pygeode import MAX_ARRAY_SIZE
  from warnings import warn
  from pygeode import svdcore as lib

  if matrix in ('cov', 'covariance'): matrix = 'cov'
  elif matrix in ('cor', 'corr', 'correlation'): matrix = 'cor'
  else:
    warn ("invalid matrix type '%'.  Defaulting to covariance."%matrix, stacklevel=2)
    matrix = 'cov'

  MAX_ITER = 1000

  # Iterate over more EOFs than we need
  # (this helps with convergence)
  # TODO: a more rigorous formula for the optimum number of EOFs to use
  if subspace <= 0: subspace = 2*num + 8
  if subspace < num: subspace = num  # Just in case

  # Remember the names
  prefix1 = var1.name+'_' if var1.name != '' else ''
  prefix2 = var2.name+'_' if var2.name != '' else ''

  # Apply weights?
#  if weight1 is not None: var1 *= weight1.sqrt()
#  if weight2 is not None: var2 *= weight2.sqrt()
  if weight1 is True: weight1 = var1.getweights()
  if weight1 is not False:
    assert not weight1.hasaxis(iaxis), "Can't handle weights along the record axis"
    # Normalize the weights
    W = weight1.sum() / weight1.size
    weight1 /= W
    # Apply the weights
    var1 *= weight1.sqrt()
  if weight2 is True: weight2 = var2.getweights()
  if weight2 is not False:
    assert not weight2.hasaxis(iaxis), "Can't handle weights along the record axis"
    # Normalize the weights
    W = weight2.sum() / weight2.size
    weight2 /= W
    # Apply the weights
    var2 *= weight2.sqrt()


  #TODO: allow multiple iteration axes (i.e., time and ensemble)
#  if iaxis is None:
#    if var1.hasaxis(Time) and var2.hasaxis(Time):
#      iaxis1 = var1.whichaxis(Time)
#      iaxis2 = var2.whichaxis(Time)
#    else:
#      iaxis1 = 0
#      iaxis2 = 0
#  else:
  iaxis1 = var1.whichaxis(iaxis)
  iaxis2 = var2.whichaxis(iaxis)

  assert var1.axes[iaxis1] == var2.axes[iaxis2], "incompatible iteration axes"
  del iaxis  # so we don't use this by accident


  # Special case: can load entire variable in memory
  # This will save some time, especially if the field is stored on disk, or is heavily derived
  if var1.size <= MAX_ARRAY_SIZE:
    print('preloading '+repr(var1))
    var1 = var1.load()
  if var2.size <= MAX_ARRAY_SIZE:
    print('preloading '+repr(var2))
    var2 = var2.load()

  # Use correlation instead of covariance?
  # (normalize by standard deviation)
  if matrix == 'cor':
    print('computing standard deviations')
    std1 = var1.stdev(iaxis1).load()
    std2 = var2.stdev(iaxis2).load()
    # account for grid points with zero standard deviation?
    std1.values = std1.values + (std1.values == 0)
    std2.values = std2.values + (std2.values == 0)
    var1 /= std1
    var2 /= std2


  eofshape1 =  (subspace,) + var1.shape[:iaxis1] + var1.shape[iaxis1+1:]
  eofshape2 =  (subspace,) + var2.shape[:iaxis2] + var2.shape[iaxis2+1:]

  pcshape1 =  (var1.shape[iaxis1], subspace)
  pcshape2 =  (var2.shape[iaxis2], subspace)

  # number of spatial grid points
  NX1 = var1.size // var1.shape[iaxis1]
  assert NX1 <= MAX_ARRAY_SIZE, 'field is too large!'
  NX2 = var2.size // var2.shape[iaxis2]
  assert NX2 <= MAX_ARRAY_SIZE, 'field is too large!'

  # Total number of timesteps
  NT = var1.shape[iaxis1]
  # Number of timesteps we can do in one fetch
  dt = MAX_ARRAY_SIZE // max(NX1,NX2)

  pcs1 = np.empty(pcshape1,dtype='d')
  pcs2 = np.empty(pcshape2,dtype='d')

  X = np.empty(eofshape2,dtype='d')
  U = np.empty(eofshape1,dtype='d')
  # Seed with sinusoids superimposed on random values
  Y = np.random.rand(*eofshape1)
  V = np.random.rand(*eofshape2)
  from math import pi
  for i in range(subspace):
    Y[i,...].reshape(NX1)[:] += np.cos( np.arange(NX1,dtype='d') / NX1 * 2 * pi * (i+1))
    V[i,...].reshape(NX2)[:] += np.cos( np.arange(NX2,dtype='d') / NX2 * 2 * pi * (i+1))

#  raise Exception

  # Workspace for C code
  UtAX  = np.empty([subspace,subspace], dtype='d')
  XtAtU = np.empty([subspace,subspace], dtype='d')
  VtV   = np.empty([subspace,subspace], dtype='d')
  YtY   = np.empty([subspace,subspace], dtype='d')

  # Views over whole variables
  # (rearranged to be compatible with our output eof arrays)
  view1 = View( (var1.axes[iaxis1],) + var1.axes[:iaxis1] + var1.axes[iaxis1+1:] )
  view2 = View( (var2.axes[iaxis2],) + var2.axes[:iaxis2] + var2.axes[iaxis2+1:] )


  for iter_num in range(1,MAX_ITER+1):

    print('iter_num: %d'%iter_num)

    assert Y.shape == U.shape
    assert X.shape == V.shape
    U, Y = Y, U
    X, V = V, X

    # Reset the accumulation arrays for the next approximations
    Y[()] = 0
    V[()] = 0

    # Apply the covariance/correlation matrix
    for t in range(0,NT,dt):
      # number of timesteps we actually have
      nt = min(dt,NT-t)

      # Read the data
      chunk1 = view1.modify_slice(0, slice(t,t+nt)).get(var1)
      chunk1 = np.ascontiguousarray(chunk1, dtype='d')
      chunk2 = view2.modify_slice(0, slice(t,t+nt)).get(var2)
      chunk2 = np.ascontiguousarray(chunk2, dtype='d')

      ier = lib.build_svds (subspace, nt, NX1, NX2, chunk1, chunk2,
                            X, Y, pcs2[t,...])
      assert ier == 0
      ier = lib.build_svds (subspace, nt, NX2, NX1, chunk2, chunk1,
                            U, V, pcs1[t,...])
      assert ier == 0


    # Useful dot products
    lib.dot(subspace, NX1, U, Y, UtAX)
    lib.dot(subspace, NX2, V, V, VtV)
    lib.dot(subspace, NX1, Y, U, XtAtU)
    lib.dot(subspace, NX1, Y, Y, YtY)

    # Compute surrogate matrices (using all available information from this iteration)
    A1, residues, rank, s = np.linalg.lstsq(UtAX,VtV,rcond=1e-30)
    A2, residues, rank, s = np.linalg.lstsq(XtAtU,YtY,rcond=1e-30)

    # Eigendecomposition on surrogate matrices
    Dy, Qy = np.linalg.eig(np.dot(A1,A2))
    Dv, Qv = np.linalg.eig(np.dot(A2,A1))

    # Sort by eigenvalue (largest first)
    S = np.argsort(np.real(Dy))[::-1]
    Dy = Dy[S]
    Qy = np.ascontiguousarray(Qy[:,S], dtype='d')
    S = np.argsort(np.real(Dv))[::-1]
    Dv = Dv[S]
    Qv = np.ascontiguousarray(Qv[:,S], dtype='d')

    # get estimate of true eigenvalues
    D = np.sqrt(Dy)  # should also = np.sqrt(Dv) in theory
    print(D)

    # Translate the surrogate eigenvectors to an estimate of the true eigenvectors
    lib.transform(subspace, NX1, Qy, Y)
    lib.transform(subspace, NX2, Qv, V)

    # Normalize
    lib.normalize (subspace, NX1, Y)
    lib.normalize (subspace, NX2, V)

    if not np.allclose(U[:num,...],Y[:num,...], atol=0): continue
    if not np.allclose(X[:num,...],V[:num,...], atol=0): continue
    print('converged after %d iterations'%iter_num)
    break

  assert iter_num != MAX_ITER, "no convergence"

  # Flip the sign of the var2 EOFs and PCs so that the covariance is positive
  lib.fixcov (subspace, NT, NX2, pcs1, pcs2, V)

  # Wrap as pygeode vars, and return
  # Only need some of the eofs for output (the rest might not have even converged yet)
  orderaxis = order(num)

  eof1 = np.array(Y[:num])
  pc1 = np.array(pcs1[...,:num]).transpose()
  eof1 = Var((orderaxis,)+var1.axes[:iaxis1]+var1.axes[iaxis1+1:], values=eof1)
  pc1 = Var((orderaxis,var1.axes[iaxis1]), values = pc1)

  eof2 = np.array(V[:num])
  pc2 = np.array(pcs2[...,:num]).transpose()
  eof2 = Var((orderaxis,)+var2.axes[:iaxis2]+var2.axes[iaxis2+1:], values=eof2)
  pc2 = Var((orderaxis,var2.axes[iaxis2]), values = pc2)

  # Apply weights?
  if weight1 is not False: eof1 /= weight1.sqrt()
  if weight2 is not False: eof2 /= weight2.sqrt()

  # Use correlation instead of covariance?
  # Re-scale the fields by standard deviation
  if matrix == 'cor':
    eof1 *= std1
    eof2 *= std2

  # Give it a name
  eof1.name = prefix1 + "EOF"
  pc1.name = prefix1 + "PC"
  eof2.name = prefix2 + "EOF"
  pc2.name = prefix2 + "PC"

  return eof1, pc1, eof2, pc2
示例#4
0
文件: eof.py 项目: weilin2018/pygeode
def EOF_iter (x, num=1, iaxis=None, subspace = -1, max_iter=1000, weight=True, out=None):
  """
  (See svd.SVD for documentation on a similar function, but replace each xxx1 and xxx2 parameter with a single xxx parameter.)
  """
  import numpy as np
  from pygeode import libpath
  from pygeode.view import View
  from math import sqrt
  from pygeode.varoperations import fill
  from pygeode import svdcore as lib

  # Need vector subspace to be at least as large as the number of EOFs extracted.
  if subspace < num: subspace = num

  # Run the single-pass guess to seed the first iteration
  guess_eof, guess_eig, guess_pc = EOF_guess (x, subspace, iaxis, weight=weight, out=None)
  # Convert NaNs to zeros so they don't screw up the matrix operations
  guess_eof = fill (guess_eof, 0)

  x, time, space = prep(var=x, iaxis=iaxis, weight=weight, out=out)
  del iaxis

  eofshape =  (subspace,) + space.shape
  pcshape =  time.shape + (subspace,)

  pcs = np.empty(pcshape,dtype='d')

  oldeofs = np.empty(eofshape,dtype='d')
  # Seed with initial guess (in the weighted space)
  neweofs = apply_weights (guess_eof, weight=weight).get()
  neweofs = np.array(neweofs, dtype='d')  # so we can write
#  neweofs = np.random.rand(*eofshape)

  # Workspace for smaller representative matrix
  work1 = np.empty([subspace,subspace], dtype='d')
  work2 = np.empty([subspace,subspace], dtype='d')

  NX = space.size

  # Variance accumulation (on first iteration only)
  variance = 0.0

  for iter_num in range(1,max_iter+1):

    print('iter_num: %d'%iter_num)

    neweofs, oldeofs = oldeofs, neweofs

    # Reset the accumulation arrays for the next approximations
    neweofs[()] = 0

    # Apply the covariance matrix
    for inview in View(x.axes).loop_mem():
      X = np.ascontiguousarray(inview.get(x), dtype='d')
      assert X.size >= space.size, "spatial pattern is too large"

      nt = inview.shape[0]
      time_offset = inview.slices[0].start
      ier = lib.build_eofs (subspace, nt, NX, X, oldeofs,
                            neweofs, pcs[time_offset,...])
      assert ier == 0

      # Compute variance?
      if iter_num == 1:
        variance += (X**2).sum()

    # Useful dot products
    lib.dot(subspace, NX, oldeofs, neweofs, work1)
    lib.dot(subspace, NX, neweofs, neweofs, work2)

    # Compute surrogate matrix (using all available information from this iteration)
    A, residues, rank, s = np.linalg.lstsq(work1,work2,rcond=1e-30)

    # Eigendecomposition on surrogate matrix
    w, P = np.linalg.eig(A)

    # Sort by eigenvalue
    S = np.argsort(w)[::-1]
    w = w[S]
    print(w)
#    assert P.dtype.name == 'float64', P.dtype.name
    P = np.ascontiguousarray(P[:,S], dtype='d')

    # Translate the surrogate eigenvectors to an estimate of the true eigenvectors
    lib.transform(subspace, NX, P, neweofs)

    # Normalize
    lib.normalize (subspace, NX, neweofs)

#    # verify orthogonality
#    for i in range(num):
#      print [np.dot(neweofs[i,...].flatten(), neweofs[j,...].flatten()) for j in range(num)]

    if np.allclose(oldeofs[:num,...],neweofs[:num,...], atol=0):
      print('converged after %d iterations'%iter_num)
      break

  assert iter_num != max_iter, "no convergence"

  # Wrap as pygeode vars, and return
  # Only need some of the eofs for output (the rest might not have even converged yet)
  eof = neweofs[:num]
  pc = pcs[...,:num].transpose()

  # Extract the eigenvalues
  # (compute magnitude of pc arrays)
  #TODO: keep eigenvalues as a separate variable in the iteration loop
  eig = np.array([sqrt( (pc[i,...]**2).sum() ) for i in range(pc.shape[0]) ])
  pc = np.dot(np.diag(1/eig), pc)

  return finalize (x, time, space, eof, eig, pc, variance, weight=weight, out=out)