CODEWITHSUNDEEP
dictionaryjulia
Mohammad Saad
Mohammad Saad

Reputation: 2005

How to change keys of a dictionary in julia?

I want to replace the values of one key of a dictionary with a column of dataframe. While the values in the second key are repeated if any of the values from first key are repeated.

For example:

using DataFrames
d = d = Dict(:1 => 2, :2=>3, :3=>4)
df = DataFrame(a = [1,1,2,2,3,3],
                b = [7,6,5,4,3,2],
                c = [9,8,7,6,6,8])

#Output
Dict{Int64,Int64} with 4 entries:
  3 => 4
  2 => 7
  1 => 6

#Dataframe
8 rows × 3 columns
a   b   c
Int64   Int64   Int64
1   7   9
1   6   8
2   5   7
2   4   6
3   3   6
3   2   8

I want to replace the keys of Dict = d with df.a, to produce the following dictionary.

Dict{Int64,Int64} with 6 entries:
 1 => 6
 1 => 6
 2 => 7
 2 => 7
 3 => 4
 3 => 4

May I know how to achieve this operation?

Update

Firstly, thanks @gTcV for the amazing suggestion and great help, highly appreciate it !!!

Just to extract the values one can follow the above post mentioned by @gTcV. However, to achieve the above dataframe operation one may use the following snippet:

using DataFrames
d = d = Dict(:1 => 2, :2=>3, :3=>4)
df = DataFrame(a = [1,1,2,2,3,3],
                b = [7,6,5,4,3,2],
                c = [9,8,7,6,6,8])
df[!, c] = [i=d[i] for i in df[:, :a]]

Output: --> 
6×3 DataFrame
 Row │ a      b      c     
     │ Int64  Int64  Int64 
─────┼─────────────────────
   1 │     1      7      2
   2 │     1      6      2
   3 │     2      5      3
   4 │     2      4      3
   5 │     3      3      4
   6 │     3      2      4

Thanks!!

Upvotes: 2

Views: 1241

Answers (1)

gTcV
gTcV

Reputation: 2504

Dicts do not allow repeated keys, so what you ask for is not possible. If it's just about the output, you can do the following:

for a in df[:,1]
    println("$a => $(d[a])")
end

Upvotes: 1

Related Questions