# Least squares example?
**URL:** https://discourse.julialang.org/t/least-squares-example/4845
**Category:** General Usage
**Tags:** linearalgebra
**Created:** [July 14, 2017, 12:49am UTC](https://discourse.julialang.org/t/least-squares-example/4845 "2017-07-14T00:49:48Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@hpoit](https://discourse.julialang.org/u/hpoit)
#### Post date: [July 14, 2017, 12:49am UTC](https://discourse.julialang.org/t/least-squares-example/4845/1 "2017-07-14T00:49:48Z")
How does this work?
```julia
julia> r = [1, 2]
2-element Array{Int64,1}:
1
2
julia> [1 2; 3 4]
2×2 Array{Int64,2}:
1 2
3 4
julia> r \ [1 2; 3 4]
1×2 Array{Float64,2}:
1.4 2.0
```
If A is a rectangular m-by-n matrix with m ~= n, and B is a matrix with m rows, then A\B returns a least-squares solution to the system of equations A\*x= B, or
If A is a scalar, then A\B is equivalent to A.\B?
I couldn’t figure out if what was stated in `?\` meant the same thing, I don’t think it did. Thanks!
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### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [July 14, 2017, 5:59am UTC](https://discourse.julialang.org/t/least-squares-example/4845/2 "2017-07-14T05:59:07Z")
`?\` has all the answers.