how to add a row number using Queryverse in Julia?
for example in R I simply use ID = row_number()
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Hi, welcome to the Julia Discourse!
i dont know if there is a function dedicated for this, but you can do:
df = DataFrame(a=[1, 2, 3], b=[:a, :b, :c]) #example dataframe
3×2 DataFrame
│ Row │ a │ b │
│ │ Int64 │ Symbol │
├─────┼───────┼────────┤
│ 1 │ 1 │ a │
│ 2 │ 2 │ b │
│ 3 │ 3 │ c │
df[!,:row_number] = 1:size(df,1) #the ! means an unsafe modification of df
julia> df
3×3 DataFrame
│ Row │ a │ b │ row_number │
│ │ Int64 │ Symbol │ Int64 │
├─────┼───────┼────────┼────────────┤
│ 1 │ 1 │ a │ 1 │
│ 2 │ 2 │ b │ 2 │
│ 3 │ 3 │ c │ 3 │
for more information about indexing, you can check here
edit: changed to size(df,1), my bad
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Thanks…but this only works when I have the following:
df[!,:row_number] = 1:size(df, 1)
otherwise, I get this error:
I think @longemen3000 meant to write size(df, 1) above - which returns the number of rows of a DataFrame (in his example there are as many rows as columns so it didn’t matter!)
Consider:
julia> using DataFrames
julia> df = DataFrame(a = rand(5), b = rand(5))
5×2 DataFrame
│ Row │ a │ b │
│ │ Float64 │ Float64 │
├─────┼──────────┼──────────┤
│ 1 │ 0.814602 │ 0.826607 │
│ 2 │ 0.361759 │ 0.631964 │
│ 3 │ 0.937936 │ 0.485979 │
│ 4 │ 0.755144 │ 0.526638 │
│ 5 │ 0.932572 │ 0.577122 │
julia> size(df, 1)
5
julia> size(df, 2)
3
You could instead use the nrow function which might be safer than remembering which dimension to call size on:
julia> df[!, :row_number] = 1:nrow(df)
1:5
julia> df
5×3 DataFrame
│ Row │ a │ b │ row_number │
│ │ Float64 │ Float64 │ Int64 │
├─────┼──────────┼──────────┼────────────┤
│ 1 │ 0.814602 │ 0.826607 │ 1 │
│ 2 │ 0.361759 │ 0.631964 │ 2 │
│ 3 │ 0.937936 │ 0.485979 │ 3 │
│ 4 │ 0.755144 │ 0.526638 │ 4 │
│ 5 │ 0.932572 │ 0.577122 │ 5 │
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or:
df.row = axes(df, 1)
For more info: ?axes
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