# CSV.read seems to expect at least 2 columns

**URL:** <https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249>\
**Category:** New to Julia\
**Tags:** csv\
**Created:** [September 26, 2023, 8:58am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249 "2023-09-26T08:58:18Z")\
**Posts on this page:** 13\
**Page:** 1

<div class="post-metadata">

**Author:** ![Axze-rgb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/axze-rgb/32/50986_2.png) [@Axze-rgb](https://discourse.julialang.org/u/Axze-rgb)\
**Post date:** [September 26, 2023, 8:58am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/1 "2023-09-26T08:58:18Z")

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Hello, I am using CSV.read to load a single column dataframe. Here is the command:

> df\_MQBZ=CSV.read(“MQBZ.hist”, DataFrame, header=false)

That works but here is the result

```
> Column1	Column2

```

> Missing String15  
> 1 missing “.”  
> 2 missing “.”  
> 3 missing “0.11702”  
> 4 missing “-0.854428”

I can select column2 only, but why is it expecting a first column to begin with? It should be able to realize the data are in a single column no?

thanks

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<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:** [September 26, 2023, 9:09am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/2 "2023-09-26T09:09:59Z")

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It doesn’t:

```julia
julia> using CSV

julia> CSV.write("onecol.csv", (x = rand(5),))
"onecol.csv"

julia> using DataFrames

julia> CSV.read("onecol.csv", DataFrame)
5×1 DataFrame
 Row │ x
     │ Float64
─────┼───────────
   1 │ 0.0121646
   2 │ 0.19368
   3 │ 0.0875001
   4 │ 0.440309
   5 │ 0.895765

```

Or put differently, the issue is with your file and/or parsing options, not CSV.jl

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<div class="post-metadata">

**Author:** ![Axze-rgb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/axze-rgb/32/50986_2.png) [@Axze-rgb](https://discourse.julialang.org/u/Axze-rgb)\
**Post date:** [September 26, 2023, 9:14am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/3 "2023-09-26T09:14:02Z")

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Thanks for the prompt answer, the problem is that I am sure I have a single column. I tested with awk

> awk ‘{print NF; exit}’ MQBZ.hist  
> 1

The data looks like this

> head MQBZ.hist  
> .  
> .  
> 0.11702  
> -0.854428  
> 0.239624  
> -0.663206  
> 0.229609  
> 0.611315  
> -0.0516864  
> -0.0172187

is it interpreting a “.” or the “-” symbol in a specific way?

---

<div class="post-metadata">

**Author:** ![Dan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dan/32/42581_2.png) [@Dan](https://discourse.julialang.org/u/Dan)\
**Post date:** [September 26, 2023, 9:20am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/4 "2023-09-26T09:20:11Z")

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> [@Axze-rgb](#):
>
> awk ‘{print NF; exit}’

This `awk` script tests only the first line.

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<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:** [September 26, 2023, 9:20am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/5 "2023-09-26T09:20:49Z")

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No. Copying your data into a simple text file:

```julia
julia> CSV.read("mqbz.csv", DataFrame)
9×1 DataFrame
 Row │ .
     │ String15
─────┼────────────
   1 │ .
   2 │ 0.11702
   3 │ -0.854428
   4 │ 0.239624
   5 │ -0.663206
   6 │ 0.229609
   7 │ 0.611315
   8 │ -0.0516864
   9 │ -0.0172187

```

---

<div class="post-metadata">

**Author:** ![Dan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dan/32/42581_2.png) [@Dan](https://discourse.julialang.org/u/Dan)\
**Post date:** [September 26, 2023, 9:23am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/6 "2023-09-26T09:23:33Z")

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> [@Axze-rgb](#):
>
> awk ‘{print NF; exit}’ MQBZ.hist  
> 1

A more appropriate `awk` command would be:

```julia
awk -F, 'BEGIN {maxnf=0} {if (NF>maxnf) {maxnf = NF}} END {print "maxnf=", maxnf}' MQBZ.hist

```

---

<div class="post-metadata">

**Author:** ![Axze-rgb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/axze-rgb/32/50986_2.png) [@Axze-rgb](https://discourse.julialang.org/u/Axze-rgb)\
**Post date:** [September 26, 2023, 9:29am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/7 "2023-09-26T09:29:51Z")

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Thanks for the improved awk but

> awk -F, ‘BEGIN {maxnf=0} {if (NF\>maxnf) {maxnf = NF}} END {print “maxnf=”, maxnf}’ MQBZ.hist  
> maxnf= 1

However, something not correct is that these data are interpreted as string instead of float, could it be the source of the error?

My data file is almost 2 million lines long so I can’t paste it here for testing

---

<div class="post-metadata">

**Author:** ![Dan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dan/32/42581_2.png) [@Dan](https://discourse.julialang.org/u/Dan)\
**Post date:** [September 26, 2023, 9:48am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/8 "2023-09-26T09:48:07Z")

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This is strange, can you give the output of:

```julia
awk -vFS="" '{for(i=1;i<=NF;i++)w[$i]++}END{for(i in w) print i,w[i]}' MQBZ.hist

```

which gives a count for each character in the file?

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<div class="post-metadata">

**Author:** ![Axze-rgb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/axze-rgb/32/50986_2.png) [@Axze-rgb](https://discourse.julialang.org/u/Axze-rgb)\
**Post date:** [September 26, 2023, 9:56am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/9 "2023-09-26T09:56:02Z")

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Sure, here it is

awk -vFS=“” ‘{for(i=1;i\<=NF;i++)w[$i]++}END{for(i in w) print i,w[i]}’ MQBZ.hist  
4 355365  
5 347440  
6 341754  
7 335825  
8 331927  
9 326924

- 365027  
620395  
. 618861  
0 626287  
1 545963  
2 423568  
3 373330

It looks like it gives indeed 2 columns, really puzzling.

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<div class="post-metadata">

**Author:** ![Dan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dan/32/42581_2.png) [@Dan](https://discourse.julialang.org/u/Dan)\
**Post date:** [September 26, 2023, 10:07am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/10 "2023-09-26T10:07:24Z")

</div>

Thanks. It would be better to surround the output with triple quotes (```) on both sides to format it better.

Now, another request, can you post the output of:

```julia
od -xc MQBZ.hist | head

```

?

---

<div class="post-metadata">

**Author:** ![Axze-rgb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/axze-rgb/32/50986_2.png) [@Axze-rgb](https://discourse.julialang.org/u/Axze-rgb)\
**Post date:** [September 26, 2023, 10:11am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/11 "2023-09-26T10:11:05Z")

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Here is the new output

````plaintext

0000000 2e20 200a 0a2e 3020 312e 3731 3230 200a
              . \n . \n 0 . 1 1 7 0 2 \n    
0000020 302d 382e 3435 3234 0a38 3020 322e 3933
          - 0 . 8 5 4 4 2 8 \n 0 . 2 3 9
0000040 3236 0a34 2d20 2e30 3636 3233 3630 200a
          6 2 4 \n - 0 . 6 6 3 2 0 6 \n    
0000060 2e30 3232 3639 3930 200a 2e30 3136 3331
          0 . 2 2 9 6 0 9 \n 0 . 6 1 1 3
0000100 3531 200a 302d 302e 3135 3836 3436 200a
          1 5 \n - 0 . 0 5 1 6 8 6 4 \n  
```
 
  
In case you would know bioinformatics , the file was generated like this (yes I made a type in the output file name). 

> bcftools query -f '[%BQBZ]\n' 0001.vcf > MQBZ.hist
````

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<div class="post-metadata">

**Author:** ![Dan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dan/32/42581_2.png) [@Dan](https://discourse.julialang.org/u/Dan)\
**Post date:** [September 26, 2023, 10:35am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/12 "2023-09-26T10:35:50Z")

</div>

Use:

```julia
df_MQBZ=CSV.read(“MQBZ.hist”, DataFrame, header=false, delim=',')

```

with the added `delim` parameter.

The reason for the problem (which I’ve reproduced) is the extra space at the beginning of each line. The space confused the delimiter auto-detect code.

The reason the problem didn’t reproduce, is that pasting the lines with a space at the beginning instructed Discourse website to format as quote and remove the initial space.

Additionally, you can get rid of the extra space character by removing it from the `bcftools` format string.

---

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**Author:** ![Axze-rgb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/axze-rgb/32/50986_2.png) [@Axze-rgb](https://discourse.julialang.org/u/Axze-rgb)\
**Post date:** [September 26, 2023, 10:39am UTC](https://discourse.julialang.org/t/csv-read-seems-to-expect-at-least-2-columns/104249/13 "2023-09-26T10:39:43Z")

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Ohhh, this is amazing. Thanks for having spent so much time to help me debug this. That works. It seems the program “bcftools” introduces spaces. I don’t know why exactly it does that, and it also confuses the type detection since the value are detected as string, but I can fix that with types=[Float64]. I can indeed remove that space, The doc contains the space but I believe it’s because they show a very specific case, and don’t show the simple case.

Again, thanks so much