Adjust fit-parameter handling for the polymer_fit plugin.
[hooke.git] / hooke / plugin / polymer_fit.py
index 09b9909f2365851dcb129bfb7a716ca9d7063a62..a4b65074bcd3e5ef57edb9e8b0e12941ab794a35 100644 (file)
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 #
-# Copyright (C) 2008-2010 Alberto Gomez-Casado
+# Copyright (C) 2008-2011 Alberto Gomez-Casado
 #                         Fabrizio Benedetti
 #                         Massimo Sandal <devicerandom@gmail.com>
 #                         W. Trevor King <wking@drexel.edu>
@@ -27,21 +27,22 @@ velocity-clamp data to various polymer models (WLC, FJC, etc.).
 """
 
 import copy
-import Queue
+from Queue import Queue
 import StringIO
 import sys
 
 import numpy
 from scipy.optimize import newton
 
-from ..command import Command, Argument, Failure
+from ..command import Command, Argument, Success, Failure
 from ..config import Setting
 from ..curve import Data
-from ..plugin import Plugin
-from ..util.fit import PoorFit, ModelFitter
 from ..util.callback import is_iterable
-from .curve import CurveArgument
-from .vclamp import scale
+from ..util.fit import PoorFit, ModelFitter
+from ..util.peak import Peak
+from ..util.si import join_data_label, split_data_label
+from . import Plugin, argument_to_setting
+from .curve import ColumnAccessCommand, ColumnAddingCommand
 
 
 kB = 1.3806503e-23  # Joules/Kelvin
@@ -230,22 +231,22 @@ class FJC (ModelFitter):
     ...     'x data (m)': x_data,
     ...     }
     >>> model = FJC(d_data, info=info, rescale=True)
-    >>> outqueue = Queue.Queue()
-    >>> Lp,a = model.fit(outqueue=outqueue)
+    >>> outqueue = Queue()
+    >>> L,a = model.fit(outqueue=outqueue)
     >>> fit_info = outqueue.get(block=False)
-    >>> model.L(Lp)  # doctest: +ELLIPSIS
-    3.500...e-08
-    >>> a  # doctest: +ELLIPSIS
-    2.499...e-10
+    >>> print L
+    3.5e-08
+    >>> print a
+    2.5e-10
 
     Fit the example data with a one-parameter fit (`L`).  We introduce
     some error in our fixed Kuhn length for fun.
 
     >>> info['Kuhn length (m)'] = 2*a
     >>> model = FJC(d_data, info=info, rescale=True)
-    >>> Lp = model.fit(outqueue=outqueue)
+    >>> L, = model.fit(outqueue=outqueue)
     >>> fit_info = outqueue.get(block=False)
-    >>> model.L(Lp)  # doctest: +ELLIPSIS
+    >>> print L  # doctest: +ELLIPSIS
     3.199...e-08
     """
     def Lp(self, L):
@@ -337,6 +338,13 @@ class FJC (ModelFitter):
         self._model_data[:] = FJC_fn(x_data, T, L, a)
         return self._model_data
 
+    def fit(self, *args, **kwargs):
+        params = super(FJC, self).fit(*args, **kwargs)
+        params[0] = self.L(params[0])  # convert Lp -> L
+        if len(params) > 1:
+            params[1] = abs(params[1])  # take the absolute value of `a`
+        return params
+
     def guess_initial_params(self, outqueue=None):
         """Guess initial fitting parameters.
 
@@ -360,22 +368,6 @@ class FJC (ModelFitter):
             return [Lp]
         return [Lp, a]
 
-    def guess_scale(self, params, outqueue=None):
-        """Guess parameter scales.
-
-        Returns
-        -------
-        Lp_scale : float
-            A guess at the reparameterized contour length scale in meters.
-        a_scale : float (optional)
-            A guess at the Kuhn length in meters.  If the length of
-            `params` is less than 2, `a_scale` is not returned.
-        """
-        Lp_scale = 1.0
-        if len(params) == 1:
-            return [Lp_scale]
-        return [Lp_scale] + [x/10.0 for x in params[1:]]
-
 
 def inverse_FJC_PEG_fn(F_data, T=300, N=1, k=150., Lp=3.58e-10, Lh=2.8e-10, dG=3., a=7e-10):
     """Inverse poly(ethylene-glycol) adjusted extended FJC model.
@@ -500,22 +492,22 @@ class FJC_PEG (ModelFitter):
     ...     'Gibbs free energy difference (Gp - Gh) (kBT)': kwargs['dG'],
     ...     }
     >>> model = FJC_PEG(d_data, info=info, rescale=True)
-    >>> outqueue = Queue.Queue()
-    >>> Nr,a = model.fit(outqueue=outqueue)
+    >>> outqueue = Queue()
+    >>> N,a = model.fit(outqueue=outqueue)
     >>> fit_info = outqueue.get(block=False)
-    >>> model.L(Nr)  # doctest: +ELLIPSIS
-    122.999...
-    >>> a  # doctest: +ELLIPSIS
-    6.999...e-10
+    >>> print N
+    123.0
+    >>> print a
+    7e-10
 
     Fit the example data with a one-parameter fit (`N`).  We introduce
     some error in our fixed Kuhn length for fun.
 
     >>> info['Kuhn length (m)'] = 2*kwargs['a']
     >>> model = FJC_PEG(d_data, info=info, rescale=True)
-    >>> Nr = model.fit(outqueue=outqueue)
+    >>> N, = model.fit(outqueue=outqueue)
     >>> fit_info = outqueue.get(block=False)
-    >>> model.L(Nr)  # doctest: +ELLIPSIS
+    >>> print N  # doctest: +ELLIPSIS
     96.931...
     """
     def Lr(self, L):
@@ -617,6 +609,13 @@ class FJC_PEG (ModelFitter):
         self._model_data[:] = FJC_PEG_fn(x_data, N=N, a=a, **kwargs)
         return self._model_data
 
+    def fit(self, *args, **kwargs):
+        params = super(FJC_PEG, self).fit(*args, **kwargs)
+        params[0] = self.L(params[0])  # convert Nr -> N
+        if len(params) > 1:
+            params[1] = abs(params[1])  # take the absolute value of `a`
+        return params
+
     def guess_initial_params(self, outqueue=None):
         """Guess initial fitting parameters.
 
@@ -644,19 +643,6 @@ class FJC_PEG (ModelFitter):
             return [Nr]
         return [Nr, a]
 
-    def guess_scale(self, params, outqueue=None):
-        """Guess parameter scales.
-
-        Returns
-        -------
-        N_scale : float
-            A guess at the section count scale in meters.
-        a_scale : float (optional)
-            A guess at the Kuhn length in meters.  If the length of
-            `params` is less than 2, `a_scale` is not returned.
-        """
-        return [x/10.0 for x in params]
-
 
 def WLC_fn(x_data, T, L, p):
     """The worm like chain interpolation model.
@@ -723,22 +709,22 @@ class WLC (ModelFitter):
     ...     'x data (m)': x_data,
     ...     }
     >>> model = WLC(d_data, info=info, rescale=True)
-    >>> outqueue = Queue.Queue()
-    >>> Lp,p = model.fit(outqueue=outqueue)
+    >>> outqueue = Queue()
+    >>> L,p = model.fit(outqueue=outqueue)
     >>> fit_info = outqueue.get(block=False)
-    >>> model.L(Lp)  # doctest: +ELLIPSIS
-    3.500...e-08
-    >>> p  # doctest: +ELLIPSIS
-    2.500...e-10
+    >>> print L
+    3.5e-08
+    >>> print p
+    2.5e-10
 
     Fit the example data with a one-parameter fit (`L`).  We introduce
     some error in our fixed persistence length for fun.
 
     >>> info['persistence length (m)'] = 2*p
     >>> model = WLC(d_data, info=info, rescale=True)
-    >>> Lp = model.fit(outqueue=outqueue)
+    >>> L, = model.fit(outqueue=outqueue)
     >>> fit_info = outqueue.get(block=False)
-    >>> model.L(Lp)  # doctest: +ELLIPSIS
+    >>> print L  # doctest: +ELLIPSIS
     3.318...e-08
     """
     def Lp(self, L):
@@ -830,6 +816,13 @@ class WLC (ModelFitter):
         self._model_data[:] = WLC_fn(x_data, T, L, p)
         return self._model_data
 
+    def fit(self, *args, **kwargs):
+        params = super(WLC, self).fit(*args, **kwargs)
+        params[0] = self.L(params[0])  # convert Lp -> L
+        if len(params) > 1:
+            params[1] = abs(params[1])  # take the absolute value of `p`
+        return params
+
     def guess_initial_params(self, outqueue=None):
         """Guess initial fitting parameters.
 
@@ -854,73 +847,63 @@ class WLC (ModelFitter):
             return [Lp]
         return [Lp, p]
 
-    def guess_scale(self, params, outqueue=None):
-        """Guess parameter scales.
-
-        Returns
-        -------
-        Lp_scale : float
-            A guess at the reparameterized contour length scale in meters.
-        p_scale : float (optional)
-            A guess at the persistence length in meters.  If the
-            length of `params` is less than 2, `p_scale` is not
-            returned.
-        """
-        Lp_scale = 1.0
-        if len(params) == 1:
-            return [Lp_scale]
-        return [Lp_scale] + [x/10.0 for x in params[1:]]
-
 
 class PolymerFitPlugin (Plugin):
     """Polymer model (WLC, FJC, etc.) fitting.
     """
     def __init__(self):
         super(PolymerFitPlugin, self).__init__(name='polymer_fit')
-        self._commands = [PolymerFitCommand(self),]
-
-    def dependencies(self):
-        return ['vclamp']
-
-    def default_settings(self):
-        return [
-            Setting(section=self.setting_section, help=self.__doc__),
-            Setting(section=self.setting_section,
-                    option='polymer model',
-                    value='WLC',
-                    help="Select the default polymer model for 'polymer fit'.  See the documentation for descriptions of available algorithms."),
-            Setting(section=self.setting_section,
-                    option='FJC Kuhn length',
-                    value=4e-10, type='float',
+        self._arguments = [  # For Command initialization
+            Argument('polymer model', default='WLC', help="""
+Select the default polymer model for 'polymer fit'.  See the
+documentation for descriptions of available algorithms.
+""".strip()),
+            Argument('FJC Kuhn length', type='float', default=4e-10,
                     help='Kuhn length in meters'),
-            Setting(section=self.setting_section,
-                    option='FJC-PEG Kuhn length',
-                    value=4e-10, type='float',
+            Argument('FJC_PEG Kuhn length', type='float', default=4e-10,
                     help='Kuhn length in meters'),
-            Setting(section=self.setting_section,
-                    option='FJC-PEG elasticity',
-                    value=150.0, type='float',
+            Argument('FJC_PEG elasticity', type='float', default=150.0,
                     help='Elasticity of a PEG segment in Newtons per meter.'),
-            Setting(section=self.setting_section,
-                    option='FJC-PEG delta G',
-                    value=3.0, type='float',
-                    help='Gibbs free energy difference between trans-trans-trans (ttt) and trans-trans-gauche (ttg) PEG states in units of kBT.'),
-            Setting(section=self.setting_section,
-                    option='FJC-PEG L_helical',
-                    value=2.8e-10, type='float',
+            Argument('FJC_PEG delta G', type='float', default=3.0, help="""
+Gibbs free energy difference between trans-trans-trans (ttt) and
+trans-trans-gauche (ttg) PEG states in units of kBT.
+""".strip()),
+            Argument('FJC_PEG L_helical', type='float', default=2.8e-10,
                     help='Contour length of PEG in the ttg state.'),
-            Setting(section=self.setting_section,
-                    option='FJC-PEG L_planar',
-                    value=3.58e-10, type='float',
+            Argument('FJC_PEG L_planar', type='float', default=3.58e-10,
                     help='Contour length of PEG in the ttt state.'),
-            Setting(section=self.setting_section,
-                    option='WLC persistence length',
-                    value=4e-10, type='float',
-                    help='Persistence length in meters'),
+            Argument('WLC persistence length', type='float', default=4e-10,
+                    help='Persistence length in meters'),            
             ]
+        self._settings = [
+            Setting(section=self.setting_section, help=self.__doc__)]
+        for argument in self._arguments:
+            self._settings.append(argument_to_setting(
+                    self.setting_section, argument))
+            argument.default = None # if argument isn't given, use the config.
+        self._input_columns = [
+            ('distance column', 'cantilever adjusted extension (m)',
+             """
+Name of the column to use as the surface position input.
+""".strip()),
+            ('deflection column', 'deflection (N)',
+             """
+Name of the column to use as the deflection input.
+""".strip()),
+            ]
+        self._commands = [
+            PolymerFitCommand(self), PolymerFitPeaksCommand(self),
+            TranslateFlatPeaksCommand(self),
+            ]
+
+    def dependencies(self):
+        return ['vclamp']
 
+    def default_settings(self):
+        return self._settings
 
-class PolymerFitCommand (Command):
+
+class PolymerFitCommand (ColumnAddingCommand):
     """Polymer model (WLC, FJC, etc.) fitting.
 
     Fits an entropic elasticity function to a given chunk of the
@@ -934,45 +917,53 @@ class PolymerFitCommand (Command):
     def __init__(self, plugin):
         super(PolymerFitCommand, self).__init__(
             name='polymer fit',
+            columns=plugin._input_columns,
+            new_columns=[
+                ('output tension column', 'polymer tension',
+                 """
+Name of the column (without units) to use as the polymer tension output.
+""".strip()),
+                ],
             arguments=[
-                CurveArgument,
-                Argument(name='block', aliases=['set'], type='int', default=0,
+                Argument(name='fit parameters info name', type='string',
+                         default='polymer fit',
                          help="""
-Data block for which the fit should be calculated.  For an
-approach/retract force curve, `0` selects the approaching curve and
-`1` selects the retracting curve.
+Name (without units) for storing the fit parameters in the `.info` dictionary.
 """.strip()),
                 Argument(name='bounds', type='point', optional=False, count=2,
                          help="""
 Indicies of points bounding the selected data.
 """.strip()),
-                ],
+                ] + plugin._arguments,
             help=self.__doc__, plugin=plugin)
 
     def _run(self, hooke, inqueue, outqueue, params):
-        scale(hooke, params['curve'], params['block'])  # TODO: is autoscaling a good idea? (explicit is better than implicit)
-        data = params['curve'].data[params['block']]
-        # HACK? rely on params['curve'] being bound to the local hooke
-        # playlist (i.e. not a copy, as you would get by passing a
-        # curve through the queue).  Ugh.  Stupid queues.  As an
-        # alternative, we could pass lookup information through the
-        # queue...
-        model = self.plugin.config['polymer model']
-        new = Data((data.shape[0], data.shape[1]+1), dtype=data.dtype)
-        new.info = copy.deepcopy(data.info)
-        new[:,:-1] = data
-        new.info['columns'].append('%s tension (N)' % model)  # TODO: WLC fit for each peak, etc.
-        z_data = data[:,data.info['columns'].index(
-                'cantilever adjusted extension (m)')]
-        d_data = data[:,data.info['columns'].index('deflection (N)')]
+        params = self._setup_params(hooke, params)
+        data = self._block(hooke, params)
+        model = params['polymer model']
+        dist_data = self._get_column(
+            hooke=hooke, params=params, column_name='distance column')
+        def_data = self._get_column(
+            hooke=hooke, params=params, column_name='deflection column')
         start,stop = params['bounds']
         tension_data,ps = self.fit_polymer_model(
-            params['curve'], z_data, d_data, start, stop, outqueue)
-        new.info['%s polymer fit parameters' % model] = ps
-        new[:,-1] = tension_data
-        params['curve'].data[params['block']] = new
-
-    def fit_polymer_model(self, curve, z_data, d_data, start, stop,
+            params, dist_data, def_data, start, stop, outqueue)
+        data.info[params['fit parameters info name']] = ps
+        data.info[params['fit parameters info name']]['model'] = model
+        self._set_column(hooke=hooke, params=params,
+                         column_name='output tension column',
+                         values=tension_data)
+
+    def _setup_params(self, hooke, params):
+        for key,value in params.items():
+            if value == None:  # Use configured default value.
+                params[key] = self.plugin.config[key]
+        name,def_unit = split_data_label(params['deflection column'])
+        params['output tension column'] = join_data_label(
+            params['output tension column'], def_unit)
+        return params
+
+    def fit_polymer_model(self, params, dist_data, def_data, start, stop,
                           outqueue=None):
         """Railyard for the `fit_*_model` family.
 
@@ -980,93 +971,203 @@ Indicies of points bounding the selected data.
         appropriate backend algorithm.
         """
         fn = getattr(self, 'fit_%s_model'
-                     % self.plugin.config['polymer model'].replace('-','_'))
-        return fn(curve, z_data, d_data, start, stop, outqueue)
+                     % params['polymer model'].replace('-','_'))
+        return fn(params, dist_data, def_data, start, stop, outqueue)
 
-    def fit_FJC_model(self, curve, z_data, d_data, start, stop,
+    def fit_FJC_model(self, params, dist_data, def_data, start, stop,
                       outqueue=None):
         """Fit the data with :class:`FJC`.
         """
         info = {
             'temperature (K)': self.plugin.config['temperature'],
-            'x data (m)': z_data[start:stop],
+            'x data (m)': dist_data[start:stop],
             }
         if True:  # TODO: optionally free persistence length
             info['Kuhn length (m)'] = (
-                self.plugin.config['FJC Kuhn length'])
-        model = FJC(d_data[start:stop], info=info, rescale=True)
-        queue = Queue.Queue()
+                params['FJC Kuhn length'])
+        model = FJC(def_data[start:stop], info=info, rescale=True)
+        queue = Queue()
         params = model.fit(outqueue=queue)
         if True:  # TODO: if Kuhn length fixed
-            params = [params]
             a = info['Kuhn length (m)']
         else:
             a = params[1]
-        Lp = params[0]
-        L = model.L(Lp)
+        L = params[0]
         T = info['temperature (K)']
         fit_info = queue.get(block=False)
-        mask = numpy.zeros(z_data.shape, dtype=numpy.bool)
-        mask[start:stop] = True
-        return [FJC_fn(z_data, T=T, L=L, a=a) * mask,
-                fit_info]
+        f_data = numpy.ones(dist_data.shape, dtype=dist_data.dtype) * numpy.nan
+        f_data[start:stop] = FJC_fn(dist_data[start:stop], T=T, L=L, a=a)
+        return [f_data, fit_info]
 
-    def fit_FJC_PEG_model(self, curve, z_data, d_data, start, stop,
+    def fit_FJC_PEG_model(self, params, dist_data, def_data, start, stop,
                           outqueue=None):
         """Fit the data with :class:`FJC_PEG`.
         """
         info = {
             'temperature (K)': self.plugin.config['temperature'],
-            'x data (m)': z_data[start:stop],
+            'x data (m)': dist_data[start:stop],
             # TODO: more info
             }
         if True:  # TODO: optionally free persistence length
             info['Kuhn length (m)'] = (
-                self.plugin.config['FJC Kuhn length'])
-        model = FJC(d_data[start:stop], info=info, rescale=True)
-        queue = Queue.Queue()
+                params['FJC Kuhn length'])
+        model = FJC_PEG(def_data[start:stop], info=info, rescale=True)
+        queue = Queue()
         params = model.fit(outqueue=queue)
         if True:  # TODO: if Kuhn length fixed
-            params = [params]
             a = info['Kuhn length (m)']
         else:
             a = params[1]
-        Nr = params[0]
-        N = model.L(Nr)
+        N = params[0]
         T = info['temperature (K)']
         fit_info = queue.get(block=False)
-        mask = numpy.zeros(z_data.shape, dtype=numpy.bool)
-        mask[start:stop] = True
-        return [FJC_PEG_fn(z_data, **kwargs) * mask,
-                fit_info]
+        f_data = numpy.ones(dist_data.shape, dtype=dist_data.dtype) * numpy.nan
+        f_data[start:stop] = FJC_PEG_fn(dist_data[start:stop], **kwargs)
+        return [f_data, fit_info]
 
-    def fit_WLC_model(self, curve, z_data, d_data, start, stop,
+    def fit_WLC_model(self, params, dist_data, def_data, start, stop,
                       outqueue=None):
         """Fit the data with :class:`WLC`.
         """
         info = {
             'temperature (K)': self.plugin.config['temperature'],
-            'x data (m)': z_data[start:stop],
+            'x data (m)': dist_data[start:stop],
             }
         if True:  # TODO: optionally free persistence length
             info['persistence length (m)'] = (
-                self.plugin.config['WLC persistence length'])
-        model = WLC(d_data[start:stop], info=info, rescale=True)
-        queue = Queue.Queue()
+                params['WLC persistence length'])
+        model = WLC(def_data[start:stop], info=info, rescale=True)
+        queue = Queue()
         params = model.fit(outqueue=queue)
         if True:  # TODO: if persistence length fixed
-            params = [params]
             p = info['persistence length (m)']
         else:
             p = params[1]
-        Lp = params[0]
-        L = model.L(Lp)
+            info['persistence length (m)'] = p
+        L = params[0]
+        info['contour length (m)'] = L
         T = info['temperature (K)']
         fit_info = queue.get(block=False)
-        mask = numpy.zeros(z_data.shape, dtype=numpy.bool)
-        mask[start:stop] = True
-        return [WLC_fn(z_data, T=T, L=L, p=p) * mask,
-                fit_info]
+        info['fit'] = fit_info
+        info.pop('x data (m)')
+        f_data = numpy.ones(dist_data.shape, dtype=dist_data.dtype) * numpy.nan
+        f_data[start:stop] = WLC_fn(dist_data[start:stop], T=T, L=L, p=p)
+        return [f_data, info]
+
+
+class PolymerFitPeaksCommand (ColumnAccessCommand):
+    """Polymer model (WLC, FJC, etc.) fitting.
+
+    Use :class:`PolymerFitCommand` to fit the each peak in a list of
+    previously determined peaks.
+    """
+    def __init__(self, plugin):
+        super(PolymerFitPeaksCommand, self).__init__(
+            name='polymer fit peaks',
+            columns=plugin._input_columns,
+            arguments=[
+                Argument(name='peak info name', type='string',
+                         default='polymer peaks',
+                         help="""
+Name for the list of peaks in the `.info` dictionary.
+""".strip()),
+                Argument(name='peak index', type='int', count=-1, default=None,
+                         help="""
+Index of the selected peak in the list of peaks.  Use `None` to fit all peaks.
+""".strip()),
+                ] + plugin._arguments,
+            help=self.__doc__, plugin=plugin)
+
+    def _run(self, hooke, inqueue, outqueue, params):
+        data = self._block(hooke, params)
+        fit_command = hooke.command_by_name['polymer fit']
+        inq = Queue()
+        outq = Queue()
+        curve = params['curve']
+        params['curve'] = None
+        p = copy.deepcopy(params)
+        p['curve'] = params['curve']
+        del(p['peak info name'])
+        del(p['peak index'])
+        for i,peak in enumerate(data.info[params['peak info name']]):
+            if params['peak index'] == None or i in params['peak index']:
+                p['bounds'] = [peak.index, peak.post_index()]
+                p['output tension column'] = peak.name
+                p['fit parameters info name'] = peak.name
+                fit_command.run(hooke, inq, outq, **p)
+            ret = outq.get()
+            if not isinstance(ret, Success):
+                raise ret
+
+
+class TranslateFlatPeaksCommand (ColumnAccessCommand):
+    """Translate flat filter peaks into polymer peaks for fitting.
+
+    Use :class:`~hooke.plugin.flatfilt.FlatPeaksCommand` creates a
+    list of peaks for regions with large derivatives.  For velocity
+    clamp measurements, these regions are usually the rebound phase
+    after a protein domain unfolds, the cantilever detaches, etc.
+    Because these features occur after the polymer loading phase, we
+    need to shift the selected regions back to align them with the
+    polymer loading regions.
+    """
+    def __init__(self, plugin):
+        super(TranslateFlatPeaksCommand, self).__init__(
+            name='flat peaks to polymer peaks',
+            columns=plugin._input_columns,
+            arguments=[
+                Argument(name='input peak info name', type='string',
+                         default='flat filter peaks',
+                         help="""
+Name for the input peaks in the `.info` dictionary.
+""".strip()),
+                Argument(name='output peak info name', type='string',
+                         default='polymer peaks',
+                         help="""
+Name for the ouptput peaks in the `.info` dictionary.
+""".strip()),
+                Argument(name='end offset', type='int', default=-1,
+                         help="""
+Number of points between the end of a new peak and the start of the old.
+""".strip()),
+                Argument(name='start fraction', type='float', default=0.2,
+                         help="""
+Place the start of the new peak at `start_fraction` from the end of
+the previous old peak to the end of the new peak.  Because the first
+new peak will have no previous old peak, it uses a distance of zero
+instead.
+""".strip()),
+            ] + plugin._arguments,
+            help=self.__doc__, plugin=plugin)
+
+    def _run(self, hooke, inqueue, outqueue, params):
+        data = self._block(hooke, params)
+        dist_data = self._get_column(
+            hooke=hooke, params=params, column_name='distance column')
+        def_data = self._get_column(
+            hooke=hooke, params=params, column_name='deflection column')
+        previous_old_stop = numpy.absolute(dist_data).argmin()
+        new = []
+        try:
+            peaks = data.info[params['input peak info name']]
+        except KeyError, e:
+            raise Failure('No value for %s in %s.info (%s): %s'
+                          % (params['input peak info name'], data.info['name'],
+                             sorted(data.info.keys()), e))
+        for i,peak in enumerate(peaks):
+            next_old_start = peak.index
+            stop = next_old_start + params['end offset'] 
+            dist_start = (
+                dist_data[previous_old_stop]
+                + params['start fraction']*(
+                    dist_data[stop] - dist_data[previous_old_stop]))
+            start = numpy.absolute(dist_data - dist_start).argmin()
+            p = Peak('polymer peak %d' % i,
+                     index=start,
+                     values=def_data[start:stop])
+            new.append(p)
+            previous_old_stop = peak.post_index()
+        data.info[params['output peak info name']] = new
 
 
 # TODO: