diff --git a/mastermsm/msm/msm.py b/mastermsm/msm/msm.py
index e8bf21e..74ffd3c 100644
--- a/mastermsm/msm/msm.py
+++ b/mastermsm/msm/msm.py
@@ -7,6 +7,7 @@
 from functools import reduce, cmp_to_key
 import itertools
 import numpy as np
+from numpy.core.numeric import normalize_axis_tuple
 import networkx as nx
 import scipy.linalg as spla
 import matplotlib.pyplot as plt
@@ -350,7 +351,7 @@ def do_count(self, sliding=True):
             self.count += self.count.transpose()
         self.keep_states, self.keep_keys = self.check_connect()
 
-    def do_trans(self, evecs=False):
+    def do_trans(self, evecs=False, normalize=False):
         """ Wrapper for transition matrix calculation.
 
         Also calculates its eigenvalues and right eigenvectors.
@@ -365,7 +366,9 @@ def do_trans(self, evecs=False):
         nkeep = len(self.keep_states)
         keep_states = self.keep_states
         count = self.count
-        self.trans = msm_lib.calc_trans(nkeep, keep_states, count)
+        ###print('ionix keep_states:',keep_states)
+        ###print('ionix count matrix:',count)
+        self.trans = msm_lib.calc_trans(nkeep, keep_states, count, normalize=normalize)
         if not evecs:
             self.tauT, self.peqT = self.calc_eigsT()
         else:
diff --git a/mastermsm/msm/msm_lib.py b/mastermsm/msm/msm_lib.py
index f5e66c8..928e171 100644
--- a/mastermsm/msm/msm_lib.py
+++ b/mastermsm/msm/msm_lib.py
@@ -2,6 +2,7 @@
 This file is part of the MasterMSM package.
 
 """
+import sys #ionix
 import copy
 import numpy as np
 import networkx as nx
@@ -536,15 +537,15 @@ def do_boots_worker(x):
     peqT = rvecsT[:,ieqT]/peqT_sum
     return tauT, peqT, trans, keep_keys
 
-def calc_trans(nkeep=None, keep_states=None, count=None):
+def calc_trans(nkeep=None, keep_states=None, count=None, normalize=False):
     """ Calculates transition matrix.
 
     Uses the maximum likelihood expression by Prinz et al.[1]_
 
     Parameters
     ----------
-    lagt : float
-        Lag time for construction of MSM.
+    normalize : boolean
+        Use method of Zimmerman et al. JCTC 2018
 
     Returns
     -------
@@ -558,11 +559,23 @@ def calc_trans(nkeep=None, keep_states=None, count=None):
     Generation and validation", J. Chem. Phys. (2011).
     """
     trans = np.zeros([nkeep, nkeep], float)
-    for i in range(nkeep):
-        ni = reduce(lambda x, y: x + y, map(lambda x:
-            count[keep_states[x]][keep_states[i]], range(nkeep)))
-        for j in range(nkeep):
-            trans[j][i] = float(count[keep_states[j]][keep_states[i]])/float(ni)
+    if normalize:
+        pseudo = 1./float(nkeep)
+        for i in range(nkeep):
+            ni = reduce(lambda x, y: x + y, map(lambda x:
+                count[keep_states[x]][keep_states[i]], range(nkeep)))
+            for j in range(nkeep):
+                trans[j][i] =  float(count[keep_states[j]][keep_states[i]]) + pseudo
+                trans[j][i] /= float(ni + pseudo)
+    else:
+        for i in range(nkeep):
+            ni = reduce(lambda x, y: x + y, map(lambda x:
+                count[x][i], range(nkeep)))
+                #ionix count[keep_states[x]][keep_states[i]], range(nkeep)))
+            if ni==0.0: print(count) #ionix
+            sys.stdout.flush()
+            for j in range(nkeep):
+                trans[j][i] = float(count[keep_states[j]][keep_states[i]])/float(ni)
     return trans
 
 def calc_rate(nkeep, trans, lagt):
diff --git a/mastermsm/trajectory/traj.py b/mastermsm/trajectory/traj.py
index 27c05da..76a8534 100644
--- a/mastermsm/trajectory/traj.py
+++ b/mastermsm/trajectory/traj.py
@@ -257,6 +257,35 @@ def discretize(self, method="rama", states=None, nbins=20,\
         elif method == "contacts_hdb":
             self.distraj = traj_lib.discrete_contacts_hdbscan(mcs, ms, self.mdt)
 
+    def tica(self, method='contacts', lagt=None):
+        """ TICA dimensionality reduction.
+
+        Parameters
+        ----------
+        method : str
+            Compute input for TICA
+        lagt   : int
+            Lag time for TICA
+        
+        Returns
+        -------
+        evals : array
+            Eigenvalues of TICA coordinate transformation
+        evecs : array
+            Eigenvectors of TICA coordinate transformation
+
+        """
+        if method == "contacts":
+            dists = md.compute_contacts(self.mdt, contacts='all', scheme='ca', periodic=True)
+            x = []
+            for dist in dists[0]:
+                x.append(dist)
+            x = np.transpose(x)
+            if lagt == None: lagt = self.dt
+            evals, evecs = traj_lib.tica_worker(x,lagt)
+            ###self.distraj = PROJECT trajectory onto TICA vectors?
+            return evals, evecs 
+
     def find_keys(self, exclude=['O']):
         """ Finds out the discrete states in the trajectory
 
diff --git a/mastermsm/trajectory/traj_lib.py b/mastermsm/trajectory/traj_lib.py
index 91257e4..0291013 100644
--- a/mastermsm/trajectory/traj_lib.py
+++ b/mastermsm/trajectory/traj_lib.py
@@ -434,3 +434,98 @@ def _shift(psi, phi):
         if psi_s[i] > 2:
             psi_s[i] -= 2*np.pi
     return phi_s, psi_s
+
+def tica_worker(x,tau,dim=2):
+    """
+    Calculate TICA components for features trajectory
+    'x' with lag time 'tau'.
+    Schultze et al. JCTC 2021
+
+    Parameters
+    -----------
+    x : array
+        Array with features for each frame of the discrete trajectory.
+    tau : int
+        Lag time corresponding to the discrete trajectory.
+    dim : int
+        Number of TICA dimensions to be computed.
+
+    Returns:
+    -------
+    evals : numpy array
+        Resulting eigenvalues
+    evecs : numpy array
+        Resulting reaction coordinates
+
+    """
+
+    # x[0] contiene la lista de los valores del
+    # primer feature para todos los frames, x[1]
+    # la lista del segundo feature, etc.
+    print('Lag time for TICA:',tau)
+
+    # compute mean free x
+    x = meanfree(x)
+    # estimate covariant symmetrized matrices
+    cmat, cmat0 = covmatsym(x,tau)
+    # solve generalized eigenvalue problem
+    #n = len(x)
+    evals, evecs = \
+        spla.eig(cmat,b=cmat0,left=True,right=False)
+        #spla.eigh(cmat,b=cmat0,eigvals_only=False,subset_by_index=[n-dim,n-1])
+
+    return evals, evecs
+
+def meanfree(x):
+    """
+    Compute mean free coordinates, i.e.
+    with zero time average.
+
+    """
+    for i,xval in enumerate(x):
+        x[i] = xval - np.mean(xval)
+    return x
+
+def covmatsym(x,tau):
+    """
+    Build symmetrized covariance
+    matrices.
+
+    """
+    cmat = np.zeros((len(x),len(x)),float)
+    for i,xval in enumerate(x):
+        for j in range(i):
+            cmat[i][j] = covmat(xval,x[j],tau)
+    cmat /= float(len(x[0])-tau)
+    cmat *= 0.5
+
+    cmat0 = np.zeros((len(x),len(x)),float)
+    for i,xval in enumerate(x):
+        for j in range(i):
+            cmat0[i][j] = covmat0(xval,x[j],tau)
+    cmat0 /= float(len(x[0])-tau)
+    cmat0 *= 0.5
+
+    return cmat, cmat0
+
+def covmat(x,y,tau):
+    """
+    Calculate covariance matrices (right).
+
+    """
+    if len(x) != len(y): sys.exit('cannot obtain covariance matrices')
+    aux = 0.0
+    for i,xval in enumerate(x):
+        aux += xval*y[i+tau] + x[i+tau]*y[i]
+        if i == (len(x)-tau-1): return aux
+
+def covmat0(x,y,tau):
+    """
+    Calculate covariance matrices (left).
+
+    """
+    if len(x) != len(y): sys.exit('cannot obtain covariance matrices')
+    aux = 0.0
+    for i,xval in enumerate(x):
+        aux += xval*y[i] + x[i+tau]*y[i+tau]
+        if i == (len(x)-tau-1): return aux