# Add new column to GeoTable from Vector
**URL:** https://discourse.julialang.org/t/add-new-column-to-geotable-from-vector/130735
**Category:** Geo
**Tags:** question
**Created:** [July 15, 2025, 9:11am UTC](https://discourse.julialang.org/t/add-new-column-to-geotable-from-vector/130735 "2025-07-15T09:11:34Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@beppi](https://discourse.julialang.org/u/beppi)
#### Post date: [July 15, 2025, 9:11am UTC](https://discourse.julialang.org/t/add-new-column-to-geotable-from-vector/130735/1 "2025-07-15T09:11:34Z")
Hey guys, new to Julia
I’ve searched so much and can’t seem to find an answer to this simple question..
How do I take a Vector, and add it as a new column to a GeoTable?
I see there is a way to create a new column (`@transform(data, :col = value)`), but this puts `value` into all rows of `data`. I want the Julia equivalent of R’s:
`data$col <- value`
The context is that I am working on some spatial function like GWR, and want to plot the spatial data with an intermediate Vector data from halfway through the function. I want to add the Vector data to the original GeoTable data (both are ordered correctly), and then plot it to get an idea of if the spatial function is displaying any strange behaviour.
Thanks!
---
### Author:  [@juliohm](https://discourse.julialang.org/u/juliohm)
#### Post date: [July 15, 2025, 10:56am UTC](https://discourse.julialang.org/t/add-new-column-to-geotable-from-vector/130735/2 "2025-07-15T10:56:44Z")
Hi @beppi , thank you for sharing the question.
The `@transform` macro broadcasts the expression, meaning the right hand side of the equal sign is interpreted as a scalar value or a function call that will be applied to a vector of values. If you can share a MWE, I can help adjusting it for you.
We wish we had a simpler method to add and mutate the GeoTable columns, but that depends on Tables.jl adding support for setindex methods:
>
>
> Currently our geospatial data types implement \`getindex\` to access the underlyin…g table of attributes and geometries. We need the same high-level interface with \`setindex!\` to save users from having to learn and use Tables.jl explicitly.
---
### Author:  [@juliohm](https://discourse.julialang.org/u/juliohm)
#### Post date: [July 15, 2025, 12:36pm UTC](https://discourse.julialang.org/t/add-new-column-to-geotable-from-vector/130735/3 "2025-07-15T12:36:16Z")
One alternative is to use `hcat` to append columns in a second geotable over the same domain:
```julia
julia> t = georef((a=rand(10,10), b=rand(10,10)))
100×3 GeoTable over 10×10 CartesianGrid
┌────────────┬────────────┬─────────────────────────────────────────────────────────────┐
│ a │ b │ geometry │
│ Continuous │ Continuous │ Quadrangle │
│ [NoUnits] │ [NoUnits] │ 🖈 Cartesian{NoDatum} │
├────────────┼────────────┼─────────────────────────────────────────────────────────────┤
│ 0.333049 │ 0.225825 │ Quadrangle((x: 0.0 m, y: 0.0 m), ..., (x: 0.0 m, y: 1.0 m)) │
│ 0.883544 │ 0.0195454 │ Quadrangle((x: 1.0 m, y: 0.0 m), ..., (x: 1.0 m, y: 1.0 m)) │
│ 0.237656 │ 0.323605 │ Quadrangle((x: 2.0 m, y: 0.0 m), ..., (x: 2.0 m, y: 1.0 m)) │
│ 0.0595238 │ 0.719109 │ Quadrangle((x: 3.0 m, y: 0.0 m), ..., (x: 3.0 m, y: 1.0 m)) │
│ 0.336137 │ 0.804514 │ Quadrangle((x: 4.0 m, y: 0.0 m), ..., (x: 4.0 m, y: 1.0 m)) │
│ 0.950602 │ 0.201641 │ Quadrangle((x: 5.0 m, y: 0.0 m), ..., (x: 5.0 m, y: 1.0 m)) │
│ 0.174771 │ 0.948179 │ Quadrangle((x: 6.0 m, y: 0.0 m), ..., (x: 6.0 m, y: 1.0 m)) │
│ 0.441083 │ 0.916776 │ Quadrangle((x: 7.0 m, y: 0.0 m), ..., (x: 7.0 m, y: 1.0 m)) │
│ 0.998553 │ 0.617604 │ Quadrangle((x: 8.0 m, y: 0.0 m), ..., (x: 8.0 m, y: 1.0 m)) │
│ ⋮ │ ⋮ │ ⋮ │
└────────────┴────────────┴─────────────────────────────────────────────────────────────┘
91 rows omitted
julia> c = rand(100)
100-element Vector{Float64}:
0.759762909560509
0.8997931717498272
0.18915208994273836
0.8566582169308061
0.19567703024115346
0.46919774219117694
0.8523343403569035
⋮
0.903176123042081
0.05117485106717701
0.8946719843259158
0.025298978908059988
0.9109253234275069
0.44359813008201976
0.01729330819684116
julia> [t georef((; c), domain(t))]
100×4 GeoTable over 10×10 CartesianGrid
┌────────────┬────────────┬────────────┬─────────────────────────────────────────────────────────────┐
│ a │ b │ c │ geometry │
│ Continuous │ Continuous │ Continuous │ Quadrangle │
│ [NoUnits] │ [NoUnits] │ [NoUnits] │ 🖈 Cartesian{NoDatum} │
├────────────┼────────────┼────────────┼─────────────────────────────────────────────────────────────┤
│ 0.333049 │ 0.225825 │ 0.759763 │ Quadrangle((x: 0.0 m, y: 0.0 m), ..., (x: 0.0 m, y: 1.0 m)) │
│ 0.883544 │ 0.0195454 │ 0.899793 │ Quadrangle((x: 1.0 m, y: 0.0 m), ..., (x: 1.0 m, y: 1.0 m)) │
│ 0.237656 │ 0.323605 │ 0.189152 │ Quadrangle((x: 2.0 m, y: 0.0 m), ..., (x: 2.0 m, y: 1.0 m)) │
│ 0.0595238 │ 0.719109 │ 0.856658 │ Quadrangle((x: 3.0 m, y: 0.0 m), ..., (x: 3.0 m, y: 1.0 m)) │
│ 0.336137 │ 0.804514 │ 0.195677 │ Quadrangle((x: 4.0 m, y: 0.0 m), ..., (x: 4.0 m, y: 1.0 m)) │
│ 0.950602 │ 0.201641 │ 0.469198 │ Quadrangle((x: 5.0 m, y: 0.0 m), ..., (x: 5.0 m, y: 1.0 m)) │
│ 0.174771 │ 0.948179 │ 0.852334 │ Quadrangle((x: 6.0 m, y: 0.0 m), ..., (x: 6.0 m, y: 1.0 m)) │
│ 0.441083 │ 0.916776 │ 0.467469 │ Quadrangle((x: 7.0 m, y: 0.0 m), ..., (x: 7.0 m, y: 1.0 m)) │
│ 0.998553 │ 0.617604 │ 0.824009 │ Quadrangle((x: 8.0 m, y: 0.0 m), ..., (x: 8.0 m, y: 1.0 m)) │
│ ⋮ │ ⋮ │ ⋮ │ ⋮ │
└────────────┴────────────┴────────────┴─────────────────────────────────────────────────────────────┘
91 rows omitted
```
That is extremely verbose, but you can create a helper function:
```julia
addcolumn(t, c) = [t georef((; c), domain(t))]
```
What we really need to do is push the Tables.jl interface forward to include a `setindex!` api. The maintainers of the interface are not very responsive, unfortunately:
>
>
> Specifically, it'd be nice if I could use some traits to determine whether I can… mutate the underlying data during row or column iteration (e.g., mutating values in DataFrameRow).
---
### Author:  [@beppi](https://discourse.julialang.org/u/beppi)
#### Post date: [July 16, 2025, 2:53am UTC](https://discourse.julialang.org/t/add-new-column-to-geotable-from-vector/130735/4 "2025-07-16T02:53:16Z")
Thanks so much for your prompt replies, the code you provided is a perfect MWE (thanks!) for my case.
Your solution works, but I managed another solution:
```julia
new_t = @transform(t, :col = 0.0)
new_t.col .= c
```
Thanks again. I can see you’ve been fighting this fight for a while based on those linked issues haha.