# BoundsError: attempt to access 0-element Array{Any,1} at index \[1\]
**URL:** https://discourse.julialang.org/t/boundserror-attempt-to-access-0-element-array-any-1-at-index-1/65360
**Category:** General Usage
**Created:** [July 27, 2021, 9:21am UTC](https://discourse.julialang.org/t/boundserror-attempt-to-access-0-element-array-any-1-at-index-1/65360 "2021-07-27T09:21:48Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@kip0d](https://discourse.julialang.org/u/kip0d)
#### Post date: [July 27, 2021, 9:21am UTC](https://discourse.julialang.org/t/boundserror-attempt-to-access-0-element-array-any-1-at-index-1/65360/1 "2021-07-27T09:21:48Z")
Hello, this is my code:
```julia
distvec = []
for indm = 1:M
global distvec
distvec[indm] = -(-Nvec[1]* px[indm]- Nvec[2]* py[indm]- Nvec[3]* pz[indm])/sqrt(Nvec[1]^2+Nvec[2]^2+Nvec[3]^2)
end
```
The error I get:
```julia
BoundsError: attempt to access 0-element Array{Any,1} at index [1]
```
How do I solve this issue?
Thank you!
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [July 27, 2021, 9:49am UTC](https://discourse.julialang.org/t/boundserror-attempt-to-access-0-element-array-any-1-at-index-1/65360/2 "2021-07-27T09:49:58Z")
You want to preallocate `distvec` to the correct length, e.g. if your numbers are floats do
```julia
distvec = zeros(M)
```
or `Array{Float64, 1}(undef, M)` if you want to leave the elements uninitialized.
---
### Author:  [@sijo](https://discourse.julialang.org/u/sijo)
#### Post date: [July 27, 2021, 9:51am UTC](https://discourse.julialang.org/t/boundserror-attempt-to-access-0-element-array-any-1-at-index-1/65360/3 "2021-07-27T09:51:24Z")
The line `distvec = []` declares an empty array, so you cannot do `distvec[1] = 0.1`. You could do `push!(distvec, 0.1)`, but it’s better to pre-allocate the array with the correct size.
Also, avoid globals as much as possible. If you put this code in a function you don’t need a global:
```julia
function f(M, Nvec, px, py, pz)
# Preallocate an array full of 0.0 (write e.g. zeros(Int, M) to choose a type different from Float64)
distvec = zeros(M)
for indm = 1:M
distvec[indm] = -(-Nvec[1]* px[indm]- Nvec[2]* py[indm]- Nvec[3]* pz[indm])/sqrt(Nvec[1]^2+Nvec[2]^2+Nvec[3]^2)
end
return distvec
end
f(5, [1,2,3], 1:5, 1:5, 1:5)
```
If you don’t want to preallocate, at least create an array with a specific type, e.g. `distvec = Float64[]` instead of `distvec = []`.
You can also use array comprehension:
```julia
M = 5
Nvec = [1,2,3]
px = py = pz = 1:M
distvec = [-(-Nvec[1]*px[indm] - Nvec[2]*py[indm] - Nvec[3]*pz[indm]) / norm(Nvec)
for indm in 1:M]
```
---
### Author:  [@kip0d](https://discourse.julialang.org/u/kip0d)
#### Post date: [July 27, 2021, 10:12am UTC](https://discourse.julialang.org/t/boundserror-attempt-to-access-0-element-array-any-1-at-index-1/65360/4 "2021-07-27T10:12:09Z")
Thank you all!