Matplotlib - Stepped histogram with already binned data

Question

I am trying to get a histogram with already binned data. I have been trying to use bar() for this, but I can\'t seem to figure out how to make it a stepped hist

Answer 1

From the accompanying source at http://matplotlib.sourceforge.net/examples/pylab_examples/histogram_demo_extended.html

here is how they drew that graph:

[snip]

and the bit you want appears to be

pylab.hist(x, bins=bins, histtype='step')
                            ^
                        right here

Edit: if you want to know how hist() works, look at the source - it's defined in matplotlib/axes.py starting at line 7407.

Looking at line 7724,

x = np.zeros( 2*len(bins), np.float )
y = np.zeros( 2*len(bins), np.float )

for N bars, bins is an numpy.ndarray of N+1 values, being the edges for each bar. They twin the values for each bar (this is what fraxel is doing with np.ravel below) and shift the datapoints half a bar left to center them

x[0::2], x[1::2] = bins, bins
x -= 0.5*(bins[1]-bins[0])

set the height of each bar, twinned but offset by one (relative to the x values) to produce the step effect

# n is an array of arrays containing the number of items per bar
patches = []    # from line 7676
for m, c in zip(n, color):
    y[1:-1:2], y[2::2] = m, m
    patches.append(self.fill(x, y, closed=False, edgecolor=c, fill=False))

and the self.fill bit is what actually draws the lines.