# Sampling from a tuple of arrays

**URL:** <https://discourse.julialang.org/t/sampling-from-a-tuple-of-arrays/33332>\
**Category:** New to Julia\
**Created:** [January 14, 2020, 5:32am UTC](https://discourse.julialang.org/t/sampling-from-a-tuple-of-arrays/33332 "2020-01-14T05:32:16Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![btrentini](https://avatars.discourse-cdn.com/v4/letter/b/6f9a4e/32.png) [@btrentini](https://discourse.julialang.org/u/btrentini)\
**Post date:** [January 14, 2020, 5:32am UTC](https://discourse.julialang.org/t/sampling-from-a-tuple-of-arrays/33332/1 "2020-01-14T05:32:16Z")

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Hi Everyone,  
I am new to Julia and this is my first post in the forum. I love the language, but I still struggle a little bit.

For example, I am using flux to train a Neural Network for MNIST and I now need to sample a percentage of my flux-oriented dataset. Let me explain:

Here’s what I do:

```julia
# Get data from MNIST 
train_x = dataset_x[:, :, 1:50_000]
train_y = dataset_y[1:50_000]

# Transform the data
train_x = reshape(train_x, (:, size(train_x,3))) |> gpu
train_y = onehotbatch(train_y ,0:9) |> gpu

# Create the training tuple that Flux accepts
trainingset = [(train_x, train_y)];

```

The above is a tuple of arrays. It has size (1,). This is apparantly the only format Flux accepts when I do:

`Flux.train!(loss_function, params(model), trainingset, optimiser)`

As mentioned, I need to sample from `trainingset` with X’s and y’s in the same order.

I am currently using

`sampling = sample(trainingset,trunc(Int, round(size(trainingset[1][1],2)*j/100)),replace=false);`

Where j is a number varying from 1 to 100 in a loop

This has two issues:

1. It complains that `replace=false`
2. if I ignore replace, it returns nothing

Any tips?

I am open to:

a) Define a new way to build a training set (although `zip(X,y)` didn’t work)  
b) Define a new way to sample from the dataset

Thanks a lot!