estimate slope and intercept for Linear1D

CHANGES.rst

@@ -14,6 +14,8 @@ New Features
 - Resetting viewer limits (via ``reset_limits`` or the zoom home button) now accounts for all visible
   data layers instead of just the reference data. [#1897]
 
+- Linear1D model component now estimates slope and intercept. [#1947]
+
 Cubeviz
 ^^^^^^^
 

jdaviz/configs/default/plugins/model_fitting/initializers.py

@@ -77,16 +77,10 @@ def initialize(self, instance, x, y):
         instance : `~astropy.modeling.Model`
             The initialized model.
         """
+        slope, intercept = np.polyfit(x.value.flatten(), y.value.flatten(), 1)
 
-        # y_range = np.max(y) - np.min(y)
-        # x_range = x[-1] - x[0]
-        # slope = y_range / x_range
-        # y0 = y[0]
-
-        y_mean = np.mean(y)
-
-        instance.slope.value = 0.0
-        instance.intercept.value = y_mean.value
+        instance.slope.value = slope
+        instance.intercept.value = intercept
 
         return instance