# BoundsError

**URL:** <https://discourse.julialang.org/t/boundserror/53961>\
**Category:** Data\
**Tags:** error\
**Created:** [January 26, 2021, 9:34am UTC](https://discourse.julialang.org/t/boundserror/53961 "2021-01-26T09:34:16Z")\
**Posts on this page:** 17\
**Page:** 1

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [January 26, 2021, 9:34am UTC](https://discourse.julialang.org/t/boundserror/53961/1 "2021-01-26T09:34:16Z")

</div>

I have created a function as

> function ShortestPath(DAG, K2Score)
> 
> for i = 1:length(K2Score)  
> ind = findall(K2Score .== 0)  
> #K2Score[1,ind] ~= root,  
> K2Score[1,ind] = 0.01
> 
> end
> 
> # Finding the root.
> 
> G = DAG  
> M,N = size[DAG]  
> k = 1  
> for i in 1:M  
> for j in 1:N  
> if G[i,j] ~= 0  
> a[1,k] = i  
> a[2,k] = j  
> k = k +1  
> end  
> end  
> end
> 
> ## 
> 
> n = k-1  
> k = 1;  
> for j in 1:N  
> flag = 0  
> for i in 1:M  
> if G[i,j] ~= 0  
> flag = 1  
> end  
> end  
> if flag .== 0  
> root[1,k] = j; # Must store all the values  
> k = k+1  
> end  
> end
> 
> ## Applying bellman algorithm
> 
> for ii = 1:length(root)
> 
> k =1  
> for i = 1:n  
> if a[1,i] .== root[1,ii]  
> b[1,k] = a[1,i]  
> b[2,k] = a[2,i]  
> k = k+1  
> end  
> end
> 
> for i = 1:n  
> if a[1,i] ~= root[1,ii]  
> b[1,k] = a[1,i]  
> b[2,k] = a[2,i]  
> k = k+1  
> end  
> end
> 
> for i = 1:M  
> for ii = 1:length(root)  
> dist[ii,i] = 20000; # infinity Value  
> end  
> end
> 
> dist[ii,root[1,ii]] = 0  
> for i = 1: M  
> for j = 1:n  
> k = dist[ii,b[1,j]] + 1  
> if k .\< dist[ii,b[2,j]]  
> dist[ii,b[2,j]] = k  
> end  
> end  
> end
> 
> ## Finding the minimum of distance
> 
> final\_dist = minimum(dist, dims = 1)
> 
> end
> 
> return final\_dist
> 
> end

And I am us

> final\_dist\_UCII\_WOMEN = ShortestPath(UCIV\_WOMEN\_DAG, UCIV\_WOMEN\_K2Score)

Throughs an error like

```julia
BoundsError: attempt to access 1×112 Array{Float64,2} at index [1, CartesianIndex{2}[CartesianIndex(1, 79), CartesianIndex(1, 82), CartesianIndex(1, 83), CartesianIndex(1, 85), CartesianIndex(1, 88), CartesianIndex(1, 91), CartesianIndex(1, 94), CartesianIndex(1, 97), CartesianIndex(1, 104)]]

Stacktrace:
 [1] throw_boundserror(::Array{Float64,2}, ::Tuple{Int64,Array{CartesianIndex{2},1}}) at .\abstractarray.jl:541
 [2] checkbounds at .\abstractarray.jl:506 [inlined]
 [3] _setindex! at .\multidimensional.jl:784 [inlined]
 [4] setindex! at .\abstractarray.jl:1153 [inlined]
 [5] ShortestPath(::Array{Float64,2}, ::Array{Float64,2}) at .\In[33]:6
 [6] top-level scope at In[34]:1
 [7] include_string(::Function, ::Module, ::String, ::String) at .\loading.jl:1091

```

The data in UCIV\_WOMEN\_K2Score is like

```julia
Tables.MatrixTable{Array{Float64,2}}:
 :Column1 [-282.75936567503123]
 :Column2 [-305.58336610157846]
 :Column3 [-292.41728385977933]
 :Column4 [-305.18462549235426]
 :Column5 [-274.38053518866104]
 :Column6 [-264.9541448871945]
 :Column7 [-220.70659792617909]
 :Column8 [-134.11407429858826]
 :Column9 [-238.25801615743833]
 :Column10 [-223.2858117418622]
 :Column11 [-297.1694634952932]
 :Column12 [-296.66690599815234]
 :Column13 [-280.3308279437817]
 :Column14 [-232.9550950909364]
 :Column15 [-232.13675627716506]
 :Column16 [-236.38528000947178]
 :Column17 [-261.930952318306]
 :Column18 [-260.73925958765756]
 :Column19 [-289.29985505843]
 :Column20 [-248.3846110642878]
 :Column21 [-265.17573796201276]
 :Column22 [-304.0344529707333]
 :Column23 [-289.8263398616875]
 :Column24 [-257.0691832080685]
 :Column25 [-291.3757440508586]
 :Column26 [-264.0948838305343]
 :Column27 [-292.5600596311132]
 :Column28 [-249.35945573391615]
 :Column29 [-81.92327266391918]
 :Column30 [-119.47535227825449]
 :Column31 [-290.87671876102786]
 :Column32 [-259.1160299476976]
 :Column33 [-274.5405597958887]
 :Column34 [-282.42420745421214]
 :Column35 [-250.5227823754762]
 :Column36 [-237.45806324419493]
 :Column37 [-311.6203721601196]
 :Column38 [-284.93117212740185]
 :Column39 [-273.39518795019046]
 :Column40 [-217.78300320183075]
 :Column41 [-251.84915951112367]
 :Column42 [-272.9138143613708]
 :Column43 [-287.4156101302241]
 :Column44 [-114.37471605094095]
 :Column45 [-161.41934549656662]
 :Column46 [-261.84687097011204]
 :Column47 [-274.9514937520016]
 :Column48 [-158.65000549478196]
 :Column49 [-109.86505012401156]
 :Column50 [-213.1359440025262]
 :Column51 [-75.29153514406694]
 :Column52 [-195.70559894473286]
 :Column53 [-213.0431581230352]
 :Column54 [-281.5760210196869]
 :Column55 [-295.204849892014]
 :Column56 [-8.409162447202561]
 :Column57 [-129.96265278868083]
 :Column58 [-199.24228981544687]
 :Column59 [-279.023929653169]
 :Column60 [-170.92260998595782]
 :Column61 [-96.28484854268876]
 :Column62 [-84.50709805496444]
 :Column63 [-28.22050948456115]
 :Column64 [-5.105945473900647]
 :Column65 [-46.82916759238583]
 :Column66 [-8.409162447202561]
 :Column67 [-8.409162447202561]
 :Column68 [-8.409162447202561]
 :Column69 [-8.409162447202561]
 :Column70 [-8.409162447202561]
 :Column71 [-15.468565275793821]
 :Column72 [-8.409162447202561]
 :Column73 [-8.409162447202561]
 :Column74 [-8.409162447202561]
 :Column75 [-8.409162447202561]
 :Column76 [-13.299511575424276]
 :Column77 [-8.409162447202561]
 :Column78 [-8.409162447202561]
 :Column79 [0.0]
 :Column80 [-8.409162447202561]
 :Column81 [-8.409162447202561]
 :Column82 [0.0]
 :Column83 [0.0]
 :Column84 [-8.409162447202561]
 :Column85 [0.0]
 :Column86 [-8.409162447202561]
 :Column87 [-8.409162447202561]
 :Column88 [0.0]
 :Column89 [-8.409162447202561]
 :Column90 [-8.409162447202561]
 :Column91 [0.0]
 :Column92 [-15.468565275793821]
 :Column93 [-15.468565275793821]
 :Column94 [0.0]
 :Column95 [-8.409162447202561]
 :Column96 [-8.409162447202561]
 :Column97 [0.0]
 :Column98 [-5.105945473900647]
 :Column99 [-5.105945473900647]
 :Column100 [-5.105945473900647]
 :Column101 [-5.105945473900647]
 :Column102 [-15.468565275793821]
 :Column103 [-5.105945473900647]
 :Column104 [0.0]
 :Column105 [-8.409162447202561]
 :Column106 [-15.468565275793821]
 :Column107 [-5.105945473900647]
 :Column108 [-5.105945473900647]
 :Column109 [-5.105945473900647]
 :Column110 [-5.105945473900647]
 :Column111 [-8.409162447202561]
 :Column112 [-15.468565275793821]

```

Please help me to figure out the problem.

Thanks

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [January 26, 2021, 1:02pm UTC](https://discourse.julialang.org/t/boundserror/53961/2 "2021-01-26T13:02:11Z")

</div>

Hi @ashwanimalviya, welcome to our community! 🎊

I recommend you look at our [list of good practices](https://discourse.julialang.org/t/psa-make-it-easier-to-help-you/14757). I think you used the blockquote instead of triple backticks to post your code and it lost its identation, making it harder to read. If you use triple backticks instead the spacing is preserved (and a monospace font is used).

If you break your code in smaller functions the error message will probably be more precise. For now it is hard to understand which exact line of your problem that is throwing the error.

Giving your code a look, I found strange that you have `M, N = size[DAG]`, did you mean `M, N = size(DAG)`? Do you have some data to test you function with that throws the same error?

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [January 26, 2021, 1:45pm UTC](https://discourse.julialang.org/t/boundserror/53961/3 "2021-01-26T13:45:57Z")

</div>

Hi @Henrique_Becker Thanks for your response. I follow your suggestion regarding use of blockquote. I recently started using Julia I follow your suggestion for small functions too.  
I am reinserting the original code

```julia
function ShortestPath(DAG, K2Score)
    
for i = 1:length(K2Score)
  ind = findall(K2Score .== 0.0)
   #K2Score[1,ind] ~= root,
      K2Score[1,ind] = 0.01
    
end

# Finding the root.
G = DAG
M,N = size(DAG)
k = 1
for i in 1:M
    for j in 1:N
        if G[i,j] ~= 0
            a[1,k] = i
            a[2,k] = j
            k = k +1
        end
    end
end

##
n = k-1
k = 1;     
for j in 1:N
    flag = 0
    for i in 1:M
        if G[i,j] ~= 0
            flag = 1
        end
    end
    if flag .== 0
        root[1,k] = j; # Must store all the values
        k = k+1
    end
end

## Applying bellman algorithm

for ii = 1:length(root)

k =1
for i = 1:n
    if a[1,i] .== root[1,ii]
        b[1,k] = a[1,i]
        b[2,k] = a[2,i]
        k = k+1
    end
end

for i = 1:n
    if a[1,i] ~= root[1,ii]
        b[1,k] = a[1,i]
        b[2,k] = a[2,i]
        k = k+1
    end
end

for i = 1:M
    for ii = 1:length(root)
    dist[ii,i] = 20000; # infinity Value 
    end
end

dist[ii,root[1,ii]] = 0
 for i = 1: M
     for j = 1:n
         k = dist[ii,b[1,j]] + 1
         if k .< dist[ii,b[2,j]]
             dist[ii,b[2,j]] = k
         end
     end
 end
## Finding the minimum of distance
final_dist = minimum(dist, dims = 1)

end
    
return final_dist
    
end

```

can you please suggest me the way to attached the input data .csv file as per your request to test the function.  
Thank you very much for taking your time.

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [January 26, 2021, 1:48pm UTC](https://discourse.julialang.org/t/boundserror/53961/4 "2021-01-26T13:48:04Z")

</div>

I think you can use [https://pastebin.com/](https://pastebin.com/) for the CSV data.

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [January 26, 2021, 2:01pm UTC](https://discourse.julialang.org/t/boundserror/53961/5 "2021-01-26T14:01:25Z")

</div>

How do I send you the data on pastebin?

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [January 26, 2021, 2:05pm UTC](https://discourse.julialang.org/t/boundserror/53961/6 "2021-01-26T14:05:42Z")

</div>

Paste the code here, press “Create new paste”, and copy here the link of the page it will redirect you.

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [January 26, 2021, 2:42pm UTC](https://discourse.julialang.org/t/boundserror/53961/7 "2021-01-26T14:42:55Z")

</div>

Hi @Henrique_Becker , I have mailed you the data. Please give your suggestion here as you feel right.  
Thanks

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [February 4, 2021, 10:25pm UTC](https://discourse.julialang.org/t/boundserror/53961/8 "2021-02-04T22:25:36Z")

</div>

@ashwanimalviya, I did not have time to dive into your problem until now.

I downloaded the CSV files, and executed:

```julia
using CSV, DataFrames

dag = CSV.read("UCIV_WOMEN_DAG.csv", DataFrame)
k2s = CSV.read("UCIV_WOMEN_K2Score.csv", DataFrame)
ShortestPath(dag, k2s)

```

This already fails at the start, with:

```julia
ERROR: MethodError: no method matching length(::DataFrame)

```

What data structures are your code expecting? How do you read them from the CSV?

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [February 11, 2021, 12:25pm UTC](https://discourse.julialang.org/t/boundserror/53961/9 "2021-02-11T12:25:30Z")

</div>

Hi @Henrique_Becker

Thanks for your reply and Sorry for my late reply. I was travelling this week.  
The function “ShortestPath” is expecting the inputs(dag, k2s) in matrix form.  
Since these inputs are also an output from different function and needs to be feed as input for ShortestPath function.

I hope you get my point.  
Please feel free to write if you need to know anything about it further.

Thanks  
Ashwani

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [February 13, 2021, 2:25pm UTC](https://discourse.julialang.org/t/boundserror/53961/10 "2021-02-13T14:25:35Z")

</div>

Ashwani,

I read the CSVs in matrix form, and started trying to put it to work, but the problems kept appearing:

1. The problem you report was easy to fix. It is just that the `ind` returned by `findall` already gives you a list of `CartesianIndex{2}`, so when you use it to index K2Score, you should not do `K2Score[1,ind]` but instead just `K2Score[ind]`.
2. After this, I found the problem that `~=` is not defined. I suppose you meant `isapprox`. However, `isapprox` needs an absolute tolerance to compare with zero (what seems to be your intent), so I guessed `0.01` was a good enough tolerance, but you may need to change this.
3. Finally, you refer to some `a` variables in your code, but your code does not define them. I had nothing to do here, as I do not know anything about them. At this point I stopped.

The code I changed is [here](https://pastebin.com/3upVpCa4).

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [February 14, 2021, 10:14pm UTC](https://discourse.julialang.org/t/boundserror/53961/11 "2021-02-14T22:14:09Z")

</div>

Hi @Henrique_Becker

Thanks for your time taken to look into the matter.  
Following your suggestion to break the code into smaller functions, I have recreated the code to solve the whole task into smaller tasks. The first and second point you have mentioned is solved in this way. Thanks.

I would like to mention that `~=` is for comparing `not equal to` in MATLAB. I have used `!=` in Julia and it is working fine.

Now, the next thing is, I want to create a matrix `a` of 2 rows and variable columns out of `DAG`

```julia
# creating vector a out of DAG
function Creat_Vector_a(DAG)
G = DAG
M,N = size(DAG)
a1 = reshape(Int64[],0,1)
a2 = reshape(Int64[],0,1)   
k = 1
for i in 1:M
    for j in 1:N
        if G[i,j]!= 0'
           a1[k] = i
           a2[k] = j
            k = k +1
                if k > N
                    break
                end
                a = [a1; a2]   

        end
    end
end
    
return a
    
end

```

I am getting the following error

```julia
BoundsError: attempt to access 0×1 Array{Int64,2} at index [1]

Stacktrace:
 [1] setindex! at .\array.jl:847 [inlined]
 [2] Creat_Vector_a(::Array{Float64,2}) at .\In[87]:13
 [3] top-level scope at In[88]:1
 [4] include_string(::Function, ::Module, ::String, ::String) at .\loading.jl:1091

```

Please help me to understand it.

Thanks

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [February 14, 2021, 11:13pm UTC](https://discourse.julialang.org/t/boundserror/53961/12 "2021-02-14T23:13:28Z")

</div>

> [@ashwanimalviya](#):
>
> `a1 = reshape(Int64[],0,1)`

The problems is that both `a1` and `a2` have no valid positions (as they have zero rows), so you cannot ever save anything inside them.

Did you read the documentation for `reshape`? What exactly you intend to do with a matrix that has **zero** rows (and one column)? Also, why would you `reshape` a just-created `Int64[]`, you do reshape to make already allocated data take another shape. If you want to allocate a matrix do it directly, i.e., `Matrix{Int64}(undef, number_of_rows, number_of_columns)` if you want uninitialized data, or `zeros(Int64, number_of_rows, number_of_columns)` if you want zeroed data.

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [February 15, 2021, 12:07am UTC](https://discourse.julialang.org/t/boundserror/53961/13 "2021-02-15T00:07:46Z")

</div>

Hi @Henrique_Becker

Thank for the correction. The code worked.  
But I am not getting the desired result.

form the previous code, I want to search in every column of `DAG` starting from `1 to N` and if `0` is not found, I want to store the index `i in a1` and `j in a2` and finally a matrix `a`.

for example,  
If there are two non zero values in column 1 of `DAG` at rows 3 and 84, then it must give me `a1[1,1] = 1, a2[1,1] = 3 and a1[1,2] = 1, a2[1,2] = 84`

in this way our matrix `a` must look like

```julia
a[1,1] = 1, a[1,2] = 1
a[2,1] = 3, a[2,2] = 84 
and so on

```

Instead of getting this result, I am getting

```julia
 :Column1 [1.0, 1.0]
 :Column2 [1.0, 2.0]
 :Column3 [1.0, 3.0]
 :Column4 [1.0, 5.0]
 :Column5 [1.0, 6.0]
 :Column6 [1.0, 7.0]
 :Column7 [1.0, 8.0]
 :Column8 [1.0, 9.0]
 :Column9 [1.0, 10.0]
 :Column10 [1.0, 11.0]
 :Column11 [1.0, 12.0]
 :Column12 [1.0, 13.0]
 :Column13 [1.0, 14.0]
 :Column14 [1.0, 15.0]
 :Column15 [1.0, 16.0]
 :Column16 [1.0, 17.0]
 :Column17 [1.0, 18.0]
 :Column18 [1.0, 19.0]
 :Column19 [1.0, 20.0]
 :Column20 [1.0, 21.0]
 :Column21 [1.0, 22.0]
 :Column22 [1.0, 23.0]
 :Column23 [1.0, 24.0]
 :Column24 [1.0, 25.0]
 :Column25 [1.0, 26.0]
 :Column26 [1.0, 27.0]
 :Column27 [1.0, 28.0]
 :Column28 [1.0, 29.0]
 :Column29 [1.0, 30.0]
 :Column30 [1.0, 31.0]
 :Column31 [1.0, 32.0]
 :Column32 [1.0, 33.0]
 :Column33 [1.0, 34.0]
 :Column34 [1.0, 35.0]
 :Column35 [1.0, 36.0]
 :Column36 [1.0, 37.0]
 :Column37 [1.0, 38.0]
 :Column38 [1.0, 39.0]
 :Column39 [1.0, 40.0]
 :Column40 [1.0, 41.0]
 :Column41 [1.0, 42.0]
 :Column42 [1.0, 43.0]
 :Column43 [1.0, 44.0]
 :Column44 [1.0, 45.0]
 :Column45 [1.0, 46.0]
 :Column46 [1.0, 47.0]
 :Column47 [1.0, 48.0]
 :Column48 [1.0, 49.0]
 :Column49 [1.0, 50.0]
 :Column50 [1.0, 51.0]
 :Column51 [1.0, 52.0]
 :Column52 [1.0, 53.0]
 :Column53 [1.0, 54.0]
 :Column54 [1.0, 55.0]
 :Column55 [1.0, 56.0]
 :Column56 [1.0, 57.0]
 :Column57 [1.0, 58.0]
 :Column58 [1.0, 59.0]
 :Column59 [1.0, 60.0]
 :Column60 [1.0, 61.0]
 :Column61 [1.0, 62.0]
 :Column62 [1.0, 63.0]
 :Column63 [1.0, 64.0]
 :Column64 [1.0, 65.0]
 :Column65 [1.0, 66.0]
 :Column66 [1.0, 67.0]
 :Column67 [1.0, 68.0]
 :Column68 [1.0, 69.0]
 :Column69 [1.0, 70.0]
 :Column70 [1.0, 71.0]
 :Column71 [1.0, 72.0]
 :Column72 [1.0, 73.0]
 :Column73 [1.0, 74.0]
 :Column74 [1.0, 75.0]
 :Column75 [1.0, 76.0]
 :Column76 [1.0, 77.0]
 :Column77 [1.0, 78.0]
 :Column78 [1.0, 79.0]
 :Column79 [1.0, 80.0]
 :Column80 [1.0, 81.0]
 :Column81 [1.0, 82.0]
 :Column82 [1.0, 83.0]
 :Column83 [1.0, 84.0]
 :Column84 [1.0, 85.0]
 :Column85 [1.0, 86.0]
 :Column86 [1.0, 87.0]
 :Column87 [1.0, 88.0]
 :Column88 [1.0, 89.0]
 :Column89 [1.0, 90.0]
 :Column90 [1.0, 91.0]
 :Column91 [1.0, 92.0]
 :Column92 [1.0, 93.0]
 :Column93 [1.0, 94.0]
 :Column94 [1.0, 95.0]
 :Column95 [1.0, 96.0]
 :Column96 [1.0, 97.0]
 :Column97 [1.0, 98.0]
 :Column98 [1.0, 99.0]
 :Column99 [1.0, 100.0]
 :Column100 [1.0, 101.0]
 :Column101 [1.0, 102.0]
 :Column102 [1.0, 103.0]
 :Column103 [1.0, 104.0]
 :Column104 [1.0, 105.0]
 :Column105 [1.0, 106.0]
 :Column106 [1.0, 107.0]
 :Column107 [1.0, 108.0]
 :Column108 [1.0, 109.0]
 :Column109 [1.0, 110.0]
 :Column110 [1.0, 111.0]
 :Column111 [1.0, 112.0]
 :Column112 [2.0, 2.0]

```

Please let me know where am I making mistake in the code.

Thanks

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [February 15, 2021, 12:13am UTC](https://discourse.julialang.org/t/boundserror/53961/14 "2021-02-15T00:13:10Z")

</div>

I have updated the code like below

```julia
# creating vector a out of DAG
function Creat_Vector_a(DAG)
G = DAG
M,N = size(DAG)
a1 = Matrix{Int64}(undef, 1, 2000)
a2 = Matrix{Int64}(undef, 1, 2000)
#b = zeros(2,N)    
k = 1
for i in 1:M
    for j in 1:N
        if G[i,j]!== 0
           a1[1,k] = i
                #push!(a1[k], i)
           a2[1,k] = j
                #push!(a2[k], j)
            k = k +1
                if k > N
                    break
                end
                a = [a1; a2]   

        end
    end
end
    
return a
    
end

```

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [February 15, 2021, 1:09pm UTC](https://discourse.julialang.org/t/boundserror/53961/15 "2021-02-15T13:09:46Z")

</div>

> [@ashwanimalviya](#):
>
> for example,  
> If there are two non zero values in column 1 of `DAG` at rows 3 and 84, then it must give me `a1[1,1] = 1, a2[1,1] = 3 and a1[1,2] = 1, a2[1,2] = 84`

Why `a1` and `a2` are matrices, or better, why `a1` and `a2` have both rows and columns, in the example you only change the second index, the first index will change in some situation? They are not better as `Vectors`? In fact, in your code you save them by using:

```julia
           a1[k] = i
           a2[k] = j

```

In other words, you only use one index, it seems to me that they are Vectors that for some reason you want to treat as Matrices. As you do not know the size of the vectors before starting you could define them as:

```julia
a1 = Int[]
a2 = Int[]

```

and then when you fill them you could instead

```julia
push!(a1, i)
push!(a2, j)

```

There is some reason to why

```julia
                if k > N
                    break
                end

```

? You do want to limit the number of nonzero entries obtained?

Also, you are making `a` with `a = [a1; a2]` every time you finda a non-zero, why? Do you not want to do this only at the end, and as they would be vectors it would be written this way:

```julia
a = [a1'; a2']

```

---

<div class="post-metadata">

**Author:** ![ashwanimalviya](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ashwanimalviya/32/22716_2.png) [@ashwanimalviya](https://discourse.julialang.org/u/ashwanimalviya)\
**Post date:** [February 15, 2021, 3:36pm UTC](https://discourse.julialang.org/t/boundserror/53961/16 "2021-02-15T15:36:21Z")

</div>

Hi @Henrique_Becker

Thanks for your clear explanation.

I followed your suggestion and updated the code as

```julia
function Creat_Vector_a(DAG)
G = DAG
M,N = size(DAG)
a1 = Int[]
a2 = Int[]   
k = 1
for i in 1:M
    for j in 1:N
        if G[i,j]!== 0               
           a1[k] = i           
           a2[k] = j               
           push!(a1, i)
           push!(a2, j)
           k = k +1
        end
            a = [a1'; a2']
    end
end
    
return a
    
end

```

I am getting the following error now

```julia
BoundsError: attempt to access 0-element Array{Int64,1} at index [1]

Stacktrace:
 [1] setindex! at .\array.jl:847 [inlined]
 [2] Creat_Vector_a(::Array{Float64,2}) at .\In[167]:12
 [3] top-level scope at In[168]:1
 [4] include_string(::Function, ::Module, ::String, ::String) at .\loading.jl:1091

```

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [February 15, 2021, 4:11pm UTC](https://discourse.julialang.org/t/boundserror/53961/17 "2021-02-15T16:11:25Z")

</div>

I know I do not explain every detail but, unfortunately, I do not have the time to do so. I ask you that you try to pick up the pieces and try to make sense of what I tell you.

> [@ashwanimalviya](#):
>
> ```julia
> a1[k] = i           
> a2[k] = j               
> push!(a1, i)
> push!(a2, j)
> 
> ```

The error happens because you are trying to save an element to position `1` when the `Vector` has zero positions (it is empty). Maybe in other languages the position would be created for you but this is not the case in Julia. My suggestion was that you should use `push!` **instead** of the attribution (i.e., `a1[k] = i` and `a2[k] = j`), so keep only the two last lines of these four. `push!` will create a new position for you (after all current positions), and save the value you passed in such position. Also, you do not need `k` anymore, because `push!` will always add the new element after the last one so you do not need to control the current position.

Finally, did you change the position of `a = [a1'; a2']`? It keeps making a lot of unnecessary effort where it is in your last code. My suggestion would be creating only in the line just before the `return a` (i.e., after closing the two loops).