# How to read each line from a file then store the values to array elements?

**URL:** <https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585>\
**Category:** General Usage\
**Created:** [August 18, 2021, 6:39am UTC](https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585 "2021-08-18T06:39:05Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![CRquantum](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/crquantum/32/27824_2.png) [@CRquantum](https://discourse.julialang.org/u/CRquantum)\
**Post date:** [August 18, 2021, 6:39am UTC](https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585/1 "2021-08-18T06:39:05Z")

</div>

Sorry for another stupid question. I have a file called Yji.txt, contents is listed below,

```
  3.29107948 3.01222513 1.81928273 1.73277408 1.01205782
  3.79643512 3.12969360 2.72422926 1.99088313 1.37971501
  2.20058980 2.03869455 2.01194312 1.25660107 0.85350759
  3.27627114 2.36889134 2.07543404 1.40830475 0.84922031
  3.06670541 2.77976809 1.96303171 1.71966277 1.26711606
  3.52942983 2.42193693 2.05404920 1.48999137 0.83146491
  3.37109577 2.41969083 2.02905938 1.50383911 0.74416147
  4.34400391 3.91427909 3.71031537 2.20110125 1.78240591
  3.39792241 2.30627896 2.24137999 1.52784113 0.85893251
  2.63109783 2.38360933 1.92420508 1.17364141 0.73957600

```

It is 10 lines, each line have 5 elements which are all Float64.  
Each of the line, the Float64 numbers are generated by Fortran or Matlab with the format,

```
5(f12.8,1x)

```

means (f12.8,1x) is repeated 5 times.  
Each of the f12.8,1x means that, the values took 12 space, and 8 of them are occupied by digits, as you can see, they all have 8 digits. The 1x means the values are separated by an additional space.  
Anyway, those values are in a txt file called Yji.txt. I am sure Julia is smart enough to read the format automatically.

Now, I want to do the following,  
I have an array a=Array{Float64,2}(undef,10,5) ,  
a[i,:] should store the 5 values at line i.

```
a = Array{Float64,2}(undef,10,5)   
for ln in eachline("Yji.txt")
 I need i to represent line number
    a[i, :] = I need to convert ln to the corresponding 5 Float64 numbers, so that they can be stored to a[i,:]
end

```

How to do that?

I read the ‘eachline’, and ‘read’ in Julia document, and googled a little though did not google very hard, but still not very clear, could anyone give some hints?

Sorry for the stupid question.

Thank you very much in advance!

---

<div class="post-metadata">

**Author:** ![Vasily\_Pisarev](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vasily_pisarev/32/7929_2.png) [@Vasily\_Pisarev](https://discourse.julialang.org/u/Vasily_Pisarev)\
**Post date:** [August 18, 2021, 6:52am UTC](https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585/2 "2021-08-18T06:52:36Z")

</div>

The easiest way is to use the [DelimitedFiles](https://docs.julialang.org/en/v1/stdlib/DelimitedFiles/) module from the standard library.

String to number conversion is done via `parse(T, str)` where `T` is the desired numeric type, and `split(str)` splits a string at whitespaces. Those are useful when your input is more noisy and cannot be handled by the standard tools for reading tables.

---

<div class="post-metadata">

**Author:** ![nilshg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nilshg/32/2283_2.png) [@nilshg](https://discourse.julialang.org/u/nilshg)\
**Post date:** [August 18, 2021, 6:53am UTC](https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585/3 "2021-08-18T06:53:05Z")

</div>

Probably easiest to do `using DelimitedFiles; readdlm("myfile.txt")`

---

<div class="post-metadata">

**Author:** ![Sukera](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@Sukera](https://discourse.julialang.org/u/Sukera)\
**Post date:** [August 18, 2021, 7:05am UTC](https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585/4 "2021-08-18T07:05:38Z")

</div>

You can use either the [`DelimitedFiles` stdlib](https://docs.julialang.org/en/v1/stdlib/DelimitedFiles/):

```julia
julia> using DelimitedFiles, CSV, DataFrames                    
                                                                
julia> dlm = readdlm("tmp.txt")                                 
10×5 Matrix{Float64}:                                           
 3.29108 3.01223 1.81928 1.73277 1.01206                    
 3.79644 3.12969 2.72423 1.99088 1.37972                    
 2.20059 2.03869 2.01194 1.2566 0.853508                   
 3.27627 2.36889 2.07543 1.4083 0.84922                    
 3.06671 2.77977 1.96303 1.71966 1.26712                    
 3.52943 2.42194 2.05405 1.48999 0.831465                   
 3.3711 2.41969 2.02906 1.50384 0.744161                   
 4.344 3.91428 3.71032 2.2011 1.78241                    
 3.39792 2.30628 2.24138 1.52784 0.858933                   
 2.6311 2.38361 1.92421 1.17364 0.739576                   

```

Or you can use [CSV.jl](https://juliahub.com/ui/Packages/CSV/HHBkp/0.8.5) and [DataFrames.jl](https://juliahub.com/ui/Packages/DataFrames/AR9oZ/1.2.2) (which will be helpful in the future, since a lot of other packages use DataFrames as well):

```julia
julia> CSV.read("tmp.txt", DataFrame, header=0, delim=" ")    
10×5 DataFrame                                                  
 Row │ Column1 Column2 Column3 Column4 Column5  
     │ String String String String Float64  
─────┼──────────────────────────────────────────────────────────
   1 │ 3.29107948 3.01222513 1.81928273 1.73277408 1.01206  
   2 │ 3.79643512 3.12969360 2.72422926 1.99088313 1.37972  
   3 │ 2.20058980 2.03869455 2.01194312 1.25660107 0.853508 
   4 │ 3.27627114 2.36889134 2.07543404 1.40830475 0.84922  
   5 │ 3.06670541 2.77976809 1.96303171 1.71966277 1.26712  
   6 │ 3.52942983 2.42193693 2.05404920 1.48999137 0.831465 
   7 │ 3.37109577 2.41969083 2.02905938 1.50383911 0.744161 
   8 │ 4.34400391 3.91427909 3.71031537 2.20110125 1.78241  
   9 │ 3.39792241 2.30627896 2.24137999 1.52784113 0.858933 
  10 │ 2.63109783 2.38360933 1.92420508 1.17364141 0.739576 

```

(The parsed numbers are the same, they’re just printed/displayed to a different precision.)

* * *

Just noticed that the autodetection of Float64 columns seems to have failed here, you can just create a DataFrame from the matrix given by `readdlm` as well:

```julia
julia> DataFrame(dlm, :auto)                        
10×5 DataFrame                                      
 Row │ x1 x2 x3 x4 x5       
     │ Float64 Float64 Float64 Float64 Float64  
─────┼──────────────────────────────────────────────
   1 │ 3.29108 3.01223 1.81928 1.73277 1.01206  
   2 │ 3.79644 3.12969 2.72423 1.99088 1.37972  
   3 │ 2.20059 2.03869 2.01194 1.2566 0.853508 
   4 │ 3.27627 2.36889 2.07543 1.4083 0.84922  
   5 │ 3.06671 2.77977 1.96303 1.71966 1.26712  
   6 │ 3.52943 2.42194 2.05405 1.48999 0.831465 
   7 │ 3.3711 2.41969 2.02906 1.50384 0.744161 
   8 │ 4.344 3.91428 3.71032 2.2011 1.78241  
   9 │ 3.39792 2.30628 2.24138 1.52784 0.858933 
  10 │ 2.6311 2.38361 1.92421 1.17364 0.739576 

```

---

<div class="post-metadata">

**Author:** ![CRquantum](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/crquantum/32/27824_2.png) [@CRquantum](https://discourse.julialang.org/u/CRquantum)\
**Post date:** [August 18, 2021, 7:07am UTC](https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585/5 "2021-08-18T07:07:00Z")

</div>

Thank you all very much @nilshg , @Vasily_Pisarev @Sukera .  
Nice, now I know I can do

```
using DelimitedFiles
a = readdlm("Yji.txt",Float64)

```

or just a = readdlm(“Yji.txt”)

However, it seems the values in the array a are all truncated to 6 digits or less,

```
 3.29108 3.01223 1.81928 1.73277 1.01206
 3.79644 3.12969 2.72423 1.99088 1.37972
 2.20059 2.03869 2.01194 1.2566 0.853508
 3.27627 2.36889 2.07543 1.4083 0.84922
 3.06671 2.77977 1.96303 1.71966 1.26712
 3.52943 2.42194 2.05405 1.48999 0.831465
 3.3711 2.41969 2.02906 1.50384 0.744161
 4.344 3.91428 3.71032 2.2011 1.78241
 3.39792 2.30628 2.24138 1.52784 0.858933
 2.6311 2.38361 1.92421 1.17364 0.739576

```

but originally they have 8 digits.  
Is there a way to keep all the digits from the original values?  
Or is it that they are not really ‘truncated’, and just displayed as less digits?

---

<div class="post-metadata">

**Author:** ![Sukera](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@Sukera](https://discourse.julialang.org/u/Sukera)\
**Post date:** [August 18, 2021, 7:20am UTC](https://discourse.julialang.org/t/how-to-read-each-line-from-a-file-then-store-the-values-to-array-elements/66585/6 "2021-08-18T07:20:17Z")

</div>

> [@CRquantum](#):
>
> but originally they have 8 digits.  
> Is there a way to keep all the digits from the original values?  
> Or is it that they are not really ‘truncated’, and just displayed as less digits?

It’s just a display thing:

```julia
julia> dlm = readdlm("tmp.txt", Float64)     
10×5 Matrix{Float64}:                        
 3.29108 3.01223 1.81928 1.73277 1.01206 
 3.79644 3.12969 2.72423 1.99088 1.37972 
 2.20059 2.03869 2.01194 1.2566 0.853508
 3.27627 2.36889 2.07543 1.4083 0.84922 
 3.06671 2.77977 1.96303 1.71966 1.26712 
 3.52943 2.42194 2.05405 1.48999 0.831465
 3.3711 2.41969 2.02906 1.50384 0.744161
 4.344 3.91428 3.71032 2.2011 1.78241 
 3.39792 2.30628 2.24138 1.52784 0.858933
 2.6311 2.38361 1.92421 1.17364 0.739576
                                             
julia> dlm[10,1]                             
2.63109783                                   

julia> show(IOContext(stdout, :compact=>false), MIME"text/plain"(), dlm
10×5 Array{Float64, 2}:                                                
 3.29107948 3.01222513 1.81928273 1.73277408 1.01205782            
 3.79643512 3.1296936 2.72422926 1.99088313 1.37971501            
 2.2005898 2.03869455 2.01194312 1.25660107 0.85350759            
 3.27627114 2.36889134 2.07543404 1.40830475 0.84922031            
 3.06670541 2.77976809 1.96303171 1.71966277 1.26711606            
 3.52942983 2.42193693 2.0540492 1.48999137 0.83146491            
 3.37109577 2.41969083 2.02905938 1.50383911 0.74416147            
 4.34400391 3.91427909 3.71031537 2.20110125 1.78240591            
 3.39792241 2.30627896 2.24137999 1.52784113 0.85893251            
 2.63109783 2.38360933 1.92420508 1.17364141 0.739576              

```