Fix off-by-1 error in subplot indexing

- hokay so matplotlib starts counting from 1 instead of 0 in this case (maybe because of matlab imitation?)

examples.py

@@ -83,7 +83,7 @@ def short_demo():
     axs.plot(x, np.cos(x))
     axs.plot(x, np.sin(x))
     fig.clear()
-    axs = fig.add_subplot(1, 1, 0)
+    axs = fig.add_subplot(1, 1, 1)
     axs.plot(x, np.sin(x)+1)
     axs.plot(x, np.cos(x)-1)
     axs.text(0, 0, 'figure cleared then re-used')

pyqtmpl/figure.py

@@ -124,10 +124,10 @@ def add_subplot(self, nrows, ncols, index, projection=None, polar=None, **kwargs
             raise NotImplementedError('projection keyword in add_subplot is not ready')
         if polar is not None and polar is not False:
             raise NotImplementedError('polar projection is not ready')
-        row = int(np.floor(index/ncols))
+        row = int(np.floor((index-1)/ncols))
         if row > (nrows-1):
             raise ValueError('index {} would be on row {}, but the last row is {}!'.format(index, row, nrows-1))
-        col = index % ncols
+        col = (index-1) % ncols
         ax = Axes(**kwargs)
         self.layout.addItem(ax, row, col)
         if self.axes is None:

pyqtmpl/pyplot.py

@@ -78,7 +78,7 @@ def pick_share(share, ii, jj, axs_):
     subplot_kw = subplot_kw if subplot_kw is not None else {}
     for i in range(nrows):
         for j in range(ncols):
-            index = i*ncols + j
+            index = i*ncols + j + 1
             axs[i, j] = fig.add_subplot(
                 nrows, ncols, index,
                 sharex=pick_share(sharex, i, j, axs), sharey=pick_share(sharey, i, j, axs),