# Error while vertically concatenating INDArrays?

**URL:** <https://community.konduit.ai/t/error-while-vertically-concatenating-indarrays/1540>\
**Category:** ND4J\
**Created:** [August 9, 2021, 12:07pm UTC](https://community.konduit.ai/t/error-while-vertically-concatenating-indarrays/1540 "2021-08-09T12:07:12Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![mCvjetko](https://avatars.discourse-cdn.com/v4/letter/m/439d5e/32.png) [@mCvjetko](https://community.konduit.ai/u/mCvjetko)\
**Post date:** [August 9, 2021, 12:07pm UTC](https://community.konduit.ai/t/error-while-vertically-concatenating-indarrays/1540/1 "2021-08-09T12:07:12Z")

</div>

Hello,

I’m trying to vertically append a row vector to an existing INDArray.

```auto
int[][] data={
                {1, 0, 0},
                {2, 0, 3},
        };
        INDArray input = Nd4j.createFromArray(data[0]);
        INDArray output = Nd4j.createFromArray(data[1]);
        input = Nd4j.vstack(input, output);
        input = Nd4j.vstack(input, output);

```

The program crashes on the last line of code, with the following error:

```auto
CONCAT op: all input arrays must have the same rank !

```

Why is the rank of input arrays important while concatenating vertically? Shouldn’t they just have the same column dimension?

Using Nd4j.concat(1, input, output) also doesn’t work, with the error being

```auto
CONCAT op: input axis must be in range [0, 0], but got 1 instead!

```

I apologize if I’m missing something very obvious…