I have two arrays, `a` and `b`, as follows:

```
a = array([[19.        ,  0.84722222],
           [49.        ,  0.86111111],
           [54.        ,  0.86666667],
           [42.        ,  0.9       ],
           [ 7.        ,  0.91111111],
           [46.        ,  0.99722222]])

b = array([[46.        ,  0.46944444],
       [49.        ,  0.59722222],
       [19.        ,  0.63611111],
       [42.        ,  0.72777778],
       [54.        ,  0.74722222],
       [ 7.        ,  0.98888889]])

```

I would like to sort `b` so that its first column matches the first column of array `a`.
My output should be

```
b = array([[19.        ,  0.63611111],
           [49.        ,  0.59722222],
           [54.        ,  0.74722222],
           [42.        ,  0.72777778],
           [ 7.        ,  0.98888889]
           [46.        ,  0.46944444]])

```