# Convert String to Float

**URL:** <https://discourse.pumas.ai/t/convert-string-to-float/944>\
**Category:** How-to\
**Created:** [September 21, 2023, 11:10pm UTC](https://discourse.pumas.ai/t/convert-string-to-float/944 "2023-09-21T23:10:42Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![MathangiCTM](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/mathangictm/32/142_2.png) [@MathangiCTM](https://discourse.pumas.ai/u/MathangiCTM)\
**Post date:** [September 21, 2023, 11:10pm UTC](https://discourse.pumas.ai/t/convert-string-to-float/944/1 "2023-09-21T23:10:42Z")

</div>

Hi,  
I have a column in a dataframe which is of type =`String15`. I need to convert that to `float`.

```auto
julia> typeof(test[!,:Conc])
Vector{String15} (alias for Array{String15, 1})

```

When I tried to convert the `Conc` variable to `float` using the below code, I get this error. Can someone help with the error, please? Not sure what I am missing. Thanks.

```auto
test[!,:Conc] = float.(test[!,:Conc])

```

Error message

```auto
ERROR: MethodError: no method matching AbstractFloat(::String15)

Closest candidates are:
  (::Type{T})(::SymbolicUtils.Symbolic) where T<:Union{AbstractFloat, Integer, Complex{<:AbstractFloat}, Complex{<:Integer}}
   @ Symbolics C:\a\PumasSystemImages\PumasSystemImages\julia_depot\packages\Symbolics\UrqtQ\src\Symbolics.jl:150
  (::Type{T})(::AbstractChar) where T<:Union{AbstractChar, Number}
   @ Base char.jl:50
  (::Type{T})(::Base.TwicePrecision) where T<:Number
   @ Base twiceprecision.jl:266
  ...

Stacktrace:
 [1] float(x::String15)
   @ Base .\float.jl:294
 [2] _broadcast_getindex_evalf
   @ .\broadcast.jl:683 [inlined]
 [3] _broadcast_getindex
   @ .\broadcast.jl:656 [inlined]
 [4] getindex
   @ .\broadcast.jl:610 [inlined]
 [5] copy
   @ .\broadcast.jl:912 [inlined]
 [6] materialize(bc::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{1}, Nothing, typeof(float), Tuple{Vector{String15}}})
   @ Base.Broadcast .\broadcast.jl:873
 [7] top-level scope

```

---

<div class="post-metadata">

**Author:** ![vijay](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/vijay/32/96_2.png) [@vijay](https://discourse.pumas.ai/u/vijay)\
**Post date:** [September 21, 2023, 11:50pm UTC](https://discourse.pumas.ai/t/convert-string-to-float/944/2 "2023-09-21T23:50:31Z")

</div>

Hi @MathangiCTM you should use `parse` or `tryparse`. Here is a short example.

```auto
julia> a = ["1", "3", "5"]
3-element Vector{String}:
 "1"
 "3"
 "5"

julia> float.(a)
ERROR: MethodError: no method matching AbstractFloat(::String)

Closest candidates are:
  (::Type{T})(::AbstractChar) where T<:Union{AbstractChar, Number}
   @ Base char.jl:50
  (::Type{T})(::Base.TwicePrecision) where T<:Number
   @ Base twiceprecision.jl:266
  (::Type{T})(::Complex) where T<:Real
   @ Base complex.jl:44
  ...

Stacktrace:
 [1] float(x::String)
   @ Base ./float.jl:294
 [2] _broadcast_getindex_evalf
   @ ./broadcast.jl:683 [inlined]
 [3] _broadcast_getindex
   @ ./broadcast.jl:656 [inlined]
 [4] getindex
   @ ./broadcast.jl:610 [inlined]
 [5] copy
   @ ./broadcast.jl:912 [inlined]
 [6] materialize(bc::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{1}, Nothing, typeof(float), Tuple{Vector{String}}})
   @ Base.Broadcast ./broadcast.jl:873
 [7] top-level scope
   @ REPL[2]:1

julia> tryparse.(Float64, a)
3-element Vector{Float64}:
 1.0
 3.0
 5.0

```

---

<div class="post-metadata">

**Author:** ![andreasnoack](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/andreasnoack/32/22_2.png) [@andreasnoack](https://discourse.pumas.ai/u/andreasnoack)\
**Post date:** [September 22, 2023, 11:31am UTC](https://discourse.pumas.ai/t/convert-string-to-float/944/3 "2023-09-22T11:31:25Z")

</div>

When you end up with a column like that, it’s often because `CSV.read` wasn’t able to figure out how to interpret something in a numerical column in the CSV file. It’s often a bit simpler to adjust the call to `CSV.read` instead of converting the columns afterwards. An example of a CSV that causes a string column is shown below. If the missing value is coded as `NA` then we’d have to tell `CSV.read`. (Just ignore the `IOBuffer` since it’s just to pass a string to `CSV.read` instead of a file)

```julia
julia> csv_string = "a,b\n1.0,2.0\n3.0,NA"
"a,b\n1.0,2.0\n3.0,NA"

julia> print(csv_string)
a,b
1.0,2.0
3.0,NA
julia> CSV.read(IOBuffer(csv_string), DataFrame)
2×2 DataFrame
 Row │ a b
     │ Float64 String3
─────┼──────────────────
   1 │ 1.0 2.0
   2 │ 3.0 NA

julia> CSV.read(IOBuffer(csv_string), DataFrame, missingstring=["NA"])
2×2 DataFrame
 Row │ a b
     │ Float64 Float64?
─────┼────────────────────
   1 │ 1.0 2.0
   2 │ 3.0 missing

```

---

<div class="post-metadata">

**Author:** ![MathangiCTM](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/mathangictm/32/142_2.png) [@MathangiCTM](https://discourse.pumas.ai/u/MathangiCTM)\
**Post date:** [September 22, 2023, 4:07pm UTC](https://discourse.pumas.ai/t/convert-string-to-float/944/4 "2023-09-22T16:07:16Z")

</div>

Thanks @vijay and @andreasnoack .  
Yes, as you pointed out, it was because of a character in the variable column, which was otherwise numeric entries. The `CSV.read` with the `missingstring` took care of the error.  
The below code in `CSV.read` using the `types`argument also worked.

```auto
test=CSV.read("../data/original/Individual Concen Data.csv", DataFrame, header=1,skipto = 3,types=Dict(:Concentration => Float64))

```