nrows = 3
ncols = 2
fig, axes = plt.subplots(nrows=nrows, ncols=ncols)
fig.tight_layout()
fig.autofmt_xdate()
idxCol = 0
idxRow = 0
keys = ('Phosphoserine', 'Phosphothreonine', 'Phosphotyrosine','N6-acetyllysine', 'Ubiquitination', 'Sumoylation')
for key in keys:
keySubset = df[df['Modification']==key]
axes[idxRow, idxCol].bar(keySubset['Year'], keySubset['Number'])
axes[idxRow,idxCol].set_title(key)
#axes[idxRow,idxCol].get_xaxis().get_major_formatter().set_useOffset(False)
axes[idxRow,idxCol].get_xaxis().get_major_formatter().set_scientific(False)
# Tell matplotlib to interpret the x-axis values as dates
#axes[idxRow,idxCol].xaxis_date()
idxCol = idxCol + 1
if idxCol % (nrows-1) == 0:
idxCol = 0
idxRow += 1