# Appending 1D Ndarray to 2D Ndarray

## Question:

I’m attempting to append a 1D array which have generated by appending elements one at a time to a 2D array as a new row in the array.

```
a = np.ones((2, 5), int)
b = np.empty((0, 5), int)
b = np.append(b, [1])
b = np.append(b, [2])
b = np.append(b, [3])
b = np.append(b, [4])
b = np.append(b, [5])
a = np.append(a, b, axis=0)
print(b)
```

I’m pretty lost as to why this code doesn’t work? They are both arrays of 5 elements, but get the following error? "ValueError: all the input arrays must have same number of dimensions"

## Answers:

a and b have different `dim`

a is (2,5) and b is (5,) reshape b to be (1,5).

Then you can append `b`

row-wise as following:

```
result=np.append(a,b.reshape(1,-1),axis=0)
```

`np.append`

is trying to concatenate a 1D array (`b`

) with a 2D array (`a`

) along a specific axis, but `b`

doesn’t have the same number of dimensions as `a`

.

use `vstack`

instead of `append`

:

```
b = np.array([1, 2, 3, 4, 5])
a = np.vstack((a, b))
```

```
b = np.array([1, 2, 3, 4, 5])
a = np.concatenate((a, b[np.newaxis, :]), axis=0)
```

In the above examples, `b`

is first reshaped to a 2D array with shape (1,5) and then concatenated to `a`

.