I have a matrix created by the following code:

```
import numpy as np
table_vals = np.random.randn(4,4).round(4) * 100

```

and I've tried to convert numbers into percentages like this:

```
>>> table_vals.astype(np.string_) + '%'
TypeError: ufunc 'add' did not contain a loop with signature matching types dtype('<U32') dtype('<U32') dtype('<U32')

```

and like this:

```
>>> np.str(table_vals) + '%'
"[[ 137.08 120.31 -55.73 43.6 ]\n [ -94.35 -105.27 -23.31 59.16]\n [-132.9 12.04 -36.69 106.52]\n [ 126.11 -91.38 -29.16 -138.01]]%"

```

but all of them failed. So what should I do?