Adding labels to stacked bar chart
<p>I'm plotting a cross-tabulation of various offices within certain categories. I'd like to put together a horizontal stacked bar chart where each office and its value is labeled. </p>

<p>Here's some example code: </p>

<pre><code>df = pd.DataFrame({'office1': pd.Series([1,np.nan,np.nan], index=['catA', 'catB', 'catC']),
              'office2': pd.Series([np.nan,8,np.nan], index=['catA', 'catB', 'catC']),
              'office3': pd.Series([12,np.nan,np.nan], index=['catA', 'catB', 'catC']),
              'office4': pd.Series([np.nan,np.nan,3], index=['catA', 'catB', 'catC']),
              'office5': pd.Series([np.nan,5,np.nan], index=['catA', 'catB', 'catC']),
              'office6': pd.Series([np.nan,np.nan,7], index=['catA', 'catB', 'catC']),
              'office7': pd.Series([3,np.nan,np.nan], index=['catA', 'catB', 'catC']),
              'office8': pd.Series([np.nan,np.nan,11], index=['catA', 'catB', 'catC']),
              'office9': pd.Series([np.nan,6,np.nan], index=['catA', 'catB', 'catC']),
              })
ax = df.plot.barh(title="Office Breakdown by Category", legend=False, figsize=(10,7), stacked=True)
</code></pre>

<p>This gives me a fine starting point: </p>

<p><a href="http://i.stack.imgur.com/d4Jeu.png" rel="nofollow"><img src="http://i.stack.imgur.com/d4Jeu.png" alt="Stacked Bar Chart Example"></a></p>

<p>However, what I'd like to have is this: 
<a href="http://i.stack.imgur.com/a3FwK.png" rel="nofollow"><img src="http://i.stack.imgur.com/a3FwK.png" alt="Bar Chart with labels"></a></p>

<p>After some research, I came up with the following code that correctly lines up labels on the 'category' axis: </p>

<pre><code>def annotateBars(row, ax=ax):
    for col in row.index:
        value = row[col]
        if (str(value) != 'nan'):
            ax.text(value/2, labeltonum(row.name), col+","+str(value))

def labeltonum(label):
    if label == 'catA':
        return 0
    elif label == 'catB':
        return 1
    elif label == 'catC':
        return 2

df.apply(annotateBars, ax=ax, axis=1)
</code></pre>

<p>But this doesn't factor in the "stacking" of the bars. I've also tried iterating through the <code>patches</code> container returned by the plot command (which can let me retrieve x &amp; y positions of each rectangle), but I then lose any connection to the office labels. </p>

<p>You could have also just changed the function <code>annotateBars()</code> to:</p>

<pre><code>def annotateBars(row, ax=ax):
    curr_value = 0 
    for col in row.index:
        value = row[col]
        if (str(value) != 'nan'):
            ax.text(curr_value + (value)/2, labeltonum(row.name), col+","+str(value), ha='center',va='center')
            curr_value += value
</code></pre>

python pandas matplotlib