PlotCurveItem now has 'step' mode for drawing histograms

Added function for generating pseudo-scatter plots (points stack in a histogram-like manner)

functions.py

@@ -1469,3 +1469,52 @@ def invertQTransform(tr):
     return QtGui.QTransform(inv[0,0], inv[0,1], inv[0,2], inv[1,0], inv[1,1], inv[1,2], inv[2,0], inv[2,1])
     
     
+def pseudoScatter(data, spacing=None, shuffle=True):
+    """
+    Used for examining the distribution of values in a set.
+    
+    Given a list of x-values, construct a set of y-values such that an x,y scatter-plot
+    will not have overlapping points (it will look similar to a histogram).
+    """
+    inds = np.arange(len(data))
+    if shuffle:
+        np.random.shuffle(inds)
+        
+    data = data[inds]
+    
+    if spacing is None:
+        spacing = 2.*np.std(data)/len(data)**0.5
+    s2 = spacing**2
+    
+    yvals = np.empty(len(data))
+    yvals[0] = 0
+    for i in range(1,len(data)):
+        x = data[i]     # current x value to be placed
+        x0 = data[:i]   # all x values already placed
+        y0 = yvals[:i]  # all y values already placed
+        y = 0
+        
+        dx = (x0-x)**2  # x-distance to each previous point
+        xmask = dx < s2  # exclude anything too far away
+        
+        if xmask.sum() > 0:
+            dx = dx[xmask]
+            dy = (s2 - dx)**0.5   
+            limits = np.empty((2,len(dy)))  # ranges of y-values to exclude
+            limits[0] = y0[xmask] - dy
+            limits[1] = y0[xmask] + dy    
+            
+            while True:
+                # ignore anything below this y-value
+                mask = limits[1] >= y
+                limits = limits[:,mask]
+                
+                # are we inside an excluded region?
+                mask = (limits[0] < y) & (limits[1] > y)
+                if mask.sum() == 0:
+                    break
+                y = limits[:,mask].max()
+        
+        yvals[i] = y
+    
+    return yvals[np.argsort(inds)]  ## un-shuffle values before returning

graphicsItems/PlotCurveItem.py

@@ -64,6 +64,7 @@ class PlotCurveItem(GraphicsObject):
             'shadowPen': None,
             'fillLevel': None,
             'brush': None,
+            'stepMode': False,
         }
         self.setClickable(kargs.get('clickable', False))
         self.setData(*args, **kargs)
@@ -223,8 +224,15 @@ class PlotCurveItem(GraphicsObject):
         
         prof.mark('copy')
         
-        if self.xData.shape != self.yData.shape:
-            raise Exception("X and Y arrays must be the same shape--got %s and %s." % (str(x.shape), str(y.shape)))
+        if 'stepMode' in kargs:
+            self.opts['stepMode'] = kargs['stepMode']
+        
+        if self.opts['stepMode'] is True:
+            if len(self.xData) != len(self.yData)+1:  ## allow difference of 1 for step mode plots
+                raise Exception("len(X) must be len(Y)+1 since stepMode=True (got %s and %s)" % (str(x.shape), str(y.shape)))
+        else:
+            if self.xData.shape != self.yData.shape:  ## allow difference of 1 for step mode plots
+                raise Exception("X and Y arrays must be the same shape--got %s and %s." % (str(x.shape), str(y.shape)))
         
         self.path = None
         self.fillPath = None
@@ -267,6 +275,29 @@ class PlotCurveItem(GraphicsObject):
         ##    0(i4)
         ##
         ## All values are big endian--pack using struct.pack('>d') or struct.pack('>i')
+        
+        if self.opts['stepMode']:
+            ## each value in the x/y arrays generates 2 points.
+            x2 = np.empty((len(x),2), dtype=x.dtype)
+            x2[:] = x[:,np.newaxis]
+            if self.opts['fillLevel'] is None:
+                x = x2.reshape(x2.size)[1:-1]
+                y2 = np.empty((len(y),2), dtype=y.dtype)
+                y2[:] = y[:,np.newaxis]
+                y = y2.reshape(y2.size)
+            else:
+                ## If we have a fill level, add two extra points at either end
+                x = x2.reshape(x2.size)
+                y2 = np.empty((len(y)+2,2), dtype=y.dtype)
+                y2[1:-1] = y[:,np.newaxis]
+                y = y2.reshape(y2.size)[1:-1]
+                y[0] = self.opts['fillLevel']
+                y[-1] = self.opts['fillLevel']
+                
+                
+            
+        
+        
         if sys.version_info[0] == 2:   ## So this is disabled for python 3... why??
             n = x.shape[0]
             # create empty array, pad with extra space on either end
@@ -324,12 +355,21 @@ class PlotCurveItem(GraphicsObject):
         pixels = self.pixelVectors()
         if pixels == (None, None):
             pixels = [Point(0,0), Point(0,0)]
-        xmin = x.min() - pixels[0].x() * lineWidth
-        xmax = x.max() + pixels[0].x() * lineWidth
-        ymin = y.min() - abs(pixels[1].y()) * lineWidth
-        ymax = y.max() + abs(pixels[1].y()) * lineWidth
-        
             
+        xmin = x.min()
+        xmax = x.max()
+        ymin = y.min()
+        ymax = y.max()
+        
+        if self.opts['fillLevel'] is not None:
+            ymin = min(ymin, self.opts['fillLevel'])
+            ymax = max(ymax, self.opts['fillLevel'])
+            
+        xmin -= pixels[0].x() * lineWidth
+        xmax += pixels[0].x() * lineWidth
+        ymin -= abs(pixels[1].y()) * lineWidth
+        ymax += abs(pixels[1].y()) * lineWidth
+        
         return QtCore.QRectF(xmin, ymin, xmax-xmin, ymax-ymin)
 
     def paint(self, p, opt, widget):