Double initial guess for the surface kink position.

The previous algorithm would fail for curves if
1) They didn't have many tension features to stretch out the range.
2) The contact slope "softened" a bit in the kink region.

For example, try it on most of the test/vclamp_picoforce data ;).

The new algorithm works perfectly on the ideal, boring curve:
    _______
   /
  /

diff --git a/hooke/plugin/vclamp.py b/hooke/plugin/vclamp.py
index 0cfad0def3bef641e9022afd56a8db13cf840b2a..88306ff44ededee715b174438cd18da374e46356 100644 (file)
--- a/hooke/plugin/vclamp.py
+++ b/hooke/plugin/vclamp.py
@@ -165,7 +165,7 @@ Minimum `fit-contact-slope/guessed-contact-slope` ratio for a "good" fit.
         left_offset = self.info['min deflection']
         middle_deflection = (self.info['min deflection']
                              + self.info['deflection range']/2.)
         left_offset = self.info['min deflection']
         middle_deflection = (self.info['min deflection']
                              + self.info['deflection range']/2.)

-        kink_position = (self._data > middle_deflection).argmax()
+        kink_position = 2*(self._data > middle_deflection).argmax()

         left_slope = ((self._data[-1] - self.info['min deflection'])
                       /kink_position)
         right_slope = 0
         left_slope = ((self._data[-1] - self.info['min deflection'])
                       /kink_position)
         right_slope = 0

diff --git a/hooke/util/fit.py b/hooke/util/fit.py
index 13606773be4417a02d9384b7ff0bfee0648929e6..6d2e30333ac4e48c2729211c738cc73e099b7e06 100644 (file)
--- a/hooke/util/fit.py
+++ b/hooke/util/fit.py
@@ -187,6 +187,12 @@ class ModelFitter (object):
         if self._rescale == True:
             params = [p*s for p,s in zip(params, self._param_scale_factors)]
         residual = self._data - self.model(params)
         if self._rescale == True:
             params = [p*s for p,s in zip(params, self._param_scale_factors)]
         residual = self._data - self.model(params)

+        if False:  # fit debugging
+            if not hasattr(self, '_i_'):
+                self._i_ = 0
+            self._data.tofile('data.%d' % self._i_, sep='\n')
+            self.model(params).tofile('model.%d' % self._i_, sep='\n')
+            self._i_ += 1

         if self._rescale == True:
             residual /= self._data_scale_factor
         return residual
         if self._rescale == True:
             residual /= self._data_scale_factor
         return residual