Julia: Convert numeric string to float or int

Question

I am trying to write numeric data pulled from a database into a Float64[]. The original data is in ::ASCIIString format, so trying to push it to the array gives the following error:

julia> push!(a, "1") ERROR: MethodError: `convert` has no method matching convert(::Type{Float64}, ::ASCIIString) This may have arisen from a call to the constructor Float64(...), since type constructors fall back to convert methods. Closest candidates are:   call{T}(::Type{T}, ::Any)   convert(::Type{Float64}, ::Int8)   convert(::Type{Float64}, ::Int16)   ...  in push! at array.jl:432 

Attempting to convert the data directly unsurprisingly throws the same error:

julia> convert(Float64, "1") ERROR: MethodError: `convert` has no method matching convert(::Type{Float64}, ::ASCIIString) This may have arisen from a call to the constructor Float64(...), since type constructors fall back to convert methods. Closest candidates are:   call{T}(::Type{T}, ::Any)   convert(::Type{Float64}, ::Int8)   convert(::Type{Float64}, ::Int16)   ... 

Given that I know the data is numeric, is there a way I can convert it before pushing?

p.s. I am using version 0.4.0

Answer 1

You can parse(Float64,"1") from a string. Or in the case of a vector

map(x->parse(Float64,x),stringvec) 

will parse the whole vector.

BTW consider using tryparse(Float64,x) instead of parse. It returns a Nullable{Float64} which is null in the case string doesn't parse well. For example:

isnull(tryparse(Float64,"33.2.1")) == true 

And usually one would want a default value in case of a parse error:

strvec = ["1.2","NA","-1e3"] map(x->(v = tryparse(Float64,x); isnull(v) ? 0.0 : get(v)),strvec) # gives [1.2,0.0,-1000.0] 

Answer 2

Use parse(Float64,"1").

See more at: parse specification