# How to extract weights from SimpleWeightedEdge (from kruskal\_mst)
**URL:** https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192
**Category:** Graphs
**Tags:** lightgraphs, graphs
**Created:** [May 17, 2022, 12:07pm UTC](https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192 "2022-05-17T12:07:41Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@JedPhillips](https://discourse.julialang.org/u/JedPhillips)
#### Post date: [May 17, 2022, 12:07pm UTC](https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192/1 "2022-05-17T12:07:41Z")
I’m trying to figure out how to interact with a minimal spanning tree object returned by Graphs.kruskal\_mst(). I just can’t figure out how to extract the resulting edge wights (or the edges).
Here’s a minimal code to show the issue:
```julia
using Distributions
using Graphs
using SimpleWeightedGraphs
using Distances
M = reshape(rand(Normal(), 100), 10, 10)
g = SimpleWeightedGraph(pairwise(Euclidean(), M, dims = 1))
my_mst = Graphs.kruskal_mst(g)
# when inspecting the object
julia> my_mst
9-element Vector{SimpleWeightedEdge{Int64, Float64}}:
Edge 2 => 8 with weight 2.3668794009593306
Edge 1 => 10 with weight 2.4514610105905223
Edge 1 => 9 with weight 2.4717071330626306
Edge 6 => 8 with weight 2.714304985226182
⋮
Edge 3 => 9 with weight 3.507507419474672
Edge 4 => 9 with weight 4.113153232605692
Edge 1 => 7 with weight 4.1630221327329044
julia> my_mst[1]
Edge 2 => 8 with weight 2.3668794009593306
```
My goal here is just to get a vector of the edge weights. I’ve tried a bunch of thing, treating it as a dictionary, trying to convert it back to a graph, trying to extract the edges, but nothing works. I’m sure it’s a simple solution but I can’t track it down.
---
### Author:  [@gdalle](https://discourse.julialang.org/u/gdalle)
#### Post date: [May 17, 2022, 12:23pm UTC](https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192/2 "2022-05-17T12:23:06Z")
Hi there!
Don’t hesitate to ask the REPL for help, it is my best friend in such cases.
```julia
julia> typeof(my_mst[1])
SimpleWeightedEdge{Int64, Float64}
help?> SimpleWeightedEdge
search: SimpleWeightedEdge SimpleWeightedGraphEdge SimpleWeightedDiGraphEdge
No documentation found.
Summary
≡≡≡≡≡≡≡≡≡
struct SimpleWeightedEdge{T<:Integer, U<:Real}
Fields
≡≡≡≡≡≡≡≡
src :: T<:Integer
dst :: T<:Integer
weight :: U<:Real
Supertype Hierarchy
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
SimpleWeightedEdge{T<:Integer, U<:Real} <: AbstractSimpleWeightedEdge{T<:Integer} <: AbstractEdge{T<:Integer} <: Any
julia> my_mst[1].weight
3.1273492392134963
```
---
### Author:  [@JedPhillips](https://discourse.julialang.org/u/JedPhillips)
#### Post date: [May 17, 2022, 12:28pm UTC](https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192/3 "2022-05-17T12:28:51Z")
> [@gdalle](#):
>
> `SimpleWeightedEdge`
Spectacular. I’m not sure I would have understand the syntax even looking at the REPL. But this definitely will help for future issues. Thanks!
---
### Author:  [@gdalle](https://discourse.julialang.org/u/gdalle)
#### Post date: [May 17, 2022, 12:30pm UTC](https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192/4 "2022-05-17T12:30:39Z")
Glad that it solved your problem, don’t hesitate to mark the answer as a solution so that others know they don’t need to pile on 😉
I deduced the solution by looking at the fields of the `SimpleWeightedEdge` type, which can be accessed with the `object.field` syntax. The help mode of the REPL, which I used to do that, can be accessed by typing `?` as the first character
---
### Author:  [@etienne\_dg](https://discourse.julialang.org/u/etienne_dg)
#### Post date: [May 17, 2022, 12:35pm UTC](https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192/5 "2022-05-17T12:35:26Z")
It’s generally considered bad practice to access internal fields directly, you should prefer the accessor `weight(e::AbstractSimpleWeightedEdge)`. The documentation can probably be improved in this regard.
---
### Author:  [@gdalle](https://discourse.julialang.org/u/gdalle)
#### Post date: [May 18, 2022, 7:19am UTC](https://discourse.julialang.org/t/how-to-extract-weights-from-simpleweightededge-from-kruskal-mst/81192/6 "2022-05-18T07:19:34Z")
Actually @JedPhillips maybe it would be better to mark the answer by @etienne_dg as the right solution