Get the value of an item in a tensor in Tensorflow.js

Question

How do I get the value out of a tensor in Tensorflow.js after specifying the index?

Answer 1

You can use datasync for this.

const newTensor = tf.tensor2d([[2,4],[5,6]]);
const tensorData = newTensor.dataSync();
console.log("data[0] is " + tensorData[0]);
console.log("data[3] is " + tensorData[3]);

https://codepen.io/anon/pen/NMKgeO?editors=1011

Answer 2

const newTensor = tf.tensor2d([[2,4], [5,6]])
newTensor.get([0]) ##returns 2
newTensor.get([3]) ##returns 6

Thankfully, all this returns a number and not a tensor.

Answer 3

You can use the following more powerful method

tensor.buffer().get(0, 0);

This will allow you index into logical coordinates of the tensor (the 2d coordinates as opposed to the flattened 1d coordinate). See the link

Answer 4

tf.Tensor.dataSync() does not retain the original shape. If you would like to preserve the shape, you can use tf.Tensor.arraySync().

Answer 5

Alternatively you can also use slice to get the value:

let value = tensor.slice([i,j], [1, 1]);

or

let value = tensor.slice([i,j], [1, 1]).arraySync()[0][0];