# How to convert an array to Matrrix of ColorTypes.Gray

**URL:** <https://discourse.julialang.org/t/how-to-convert-an-array-to-matrrix-of-colortypes-gray/20030>\
**Category:** New to Julia\
**Created:** [January 24, 2019, 11:56am UTC](https://discourse.julialang.org/t/how-to-convert-an-array-to-matrrix-of-colortypes-gray/20030 "2019-01-24T11:56:56Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![xiaodai](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/xiaodai/32/15937_2.png) [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Post date:** [January 24, 2019, 11:56am UTC](https://discourse.julialang.org/t/how-to-convert-an-array-to-matrrix-of-colortypes-gray/20030/1 "2019-01-24T11:56:56Z")

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```julia
using Flux, Flux.Data.MNIST, Statistics
using Flux: onehotbatch, onecold, crossentropy, throttle
using Base.Iterators: repeated, partition

# load the images
imgs = MNIST.images()
raw_labels=MNIST.labels()
# average the values in the image
imgs0 = imgs[raw_labels .== 0]
avg_imgs0 = reduce(+, float.(imgs0))./length(imgs0)

```

I see that `eltype(imgs[1])` is `ColorTypes.Gray{FixedPointNumbers.Normed{UInt8,8}}` and `imgs[1]` is a 28x28 matrix. But I can’t seem to convert `avg_imgs0` which has `eltype` of `Float` back to `imgs[1]`'s eltype

I tried

```julia
#import Base.ColorTypes
ColorTypes.Gray{FixedPointNumbers.Normed{UInt8,8}}.(avg_imgs0)

```

How do I convert `avg_imgs0` back to a matrix containing `ColorTypes.Gray{FixedPointNumbers.Normed{UInt8,8}}`?

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<div class="post-metadata">

**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [January 24, 2019, 12:09pm UTC](https://discourse.julialang.org/t/how-to-convert-an-array-to-matrrix-of-colortypes-gray/20030/2 "2019-01-24T12:09:22Z")

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Please try run your code.

What is `raw_labels`. What is `Base.ColorTypes`?

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<div class="post-metadata">

**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [January 24, 2019, 12:12pm UTC](https://discourse.julialang.org/t/how-to-convert-an-array-to-matrrix-of-colortypes-gray/20030/3 "2019-01-24T12:12:10Z")

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Anyway, you can do `Gray.(avg_imgs0)`.

![Capture](https://global.discourse-cdn.com/julialang/original/3X/3/2/326d79f2c850913c63f281a8fbaf269a05a58d1b.png)

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<div class="post-metadata">

**Author:** ![xiaodai](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/xiaodai/32/15937_2.png) [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Post date:** [January 26, 2019, 1:51am UTC](https://discourse.julialang.org/t/how-to-convert-an-array-to-matrrix-of-colortypes-gray/20030/4 "2019-01-26T01:51:41Z")

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> [@kristoffer.carlsson](#):
>
> What is `raw_labels` . What is `Base.ColorTypes` ?

I’ve fixed my code, but

> [@kristoffer.carlsson](#):
>
> Anyway, you can do `Gray.(avg_imgs0)` .

Gives error `UnderVarError: Gray not defined`.

I am using Julia v1.1

---

<div class="post-metadata">

**Author:** ![xiaodai](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/xiaodai/32/15937_2.png) [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Post date:** [January 26, 2019, 1:56am UTC](https://discourse.julialang.org/t/how-to-convert-an-array-to-matrrix-of-colortypes-gray/20030/5 "2019-01-26T01:56:29Z")

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> [@kristoffer.carlsson](#):
>
> Anyway, you can do `Gray.(avg_imgs0)` .

This seems to work

```julia
]add ColorTypes
using ColorTypes
Gray.(avg_imgs0)

```