# Absolute value error?
**URL:** https://discourse.julialang.org/t/absolute-value-error/87579
**Category:** New to Julia
**Created:** [September 21, 2022, 3:14pm UTC](https://discourse.julialang.org/t/absolute-value-error/87579 "2022-09-21T15:14:12Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@ejlongman](https://discourse.julialang.org/u/ejlongman)
#### Post date: [September 21, 2022, 3:14pm UTC](https://discourse.julialang.org/t/absolute-value-error/87579/1 "2022-09-21T15:14:13Z")
Hello! I am using value function iteration to maximize a Bellman equation. When I check the difference between two vectors then take the absolute value, I get an error from the “di” line:
```julia
subt = vnew - v
println(subt)
di = abs.(subt)
v = vnew
```
For context, “subt” looks like:
[41474.08152719693 46131.513156937144; 42846.34653896693 47535.076846955286; 45098.84448852737
MethodError: no method matching isless(::Float64, ::Matrix{Float64})
Closest candidates are:
isless(::T, ::T) where T\<:Union{Float16, Float32, Float64} at /Applications/Julia-1.7.app/Contents/Resources/julia/share/julia/base/float.jl:460
isless(::AbstractFloat, ::AbstractFloat) at /Applications/Julia-1.7.app/Contents/Resources/julia/share/julia/base/operators.jl:184
isless(::Real, ::AbstractFloat) at /Applications/Julia-1.7.app/Contents/Resources/julia/share/julia/base/operators.jl:185
But
---
### Author:  [@jlapeyre](https://discourse.julialang.org/u/jlapeyre)
#### Post date: [September 21, 2022, 3:35pm UTC](https://discourse.julialang.org/t/absolute-value-error/87579/2 "2022-09-21T15:35:53Z")
It’s probably not hard to track this down. Maybe someone else can see the issue already; I don’t. Some things that might help
- the expression for `subt` that you gave is incomplete. What is the full expression?
- You wrote “But”… Is something missing?
---
### Author:  [@ctkelley](https://discourse.julialang.org/u/ctkelley)
#### Post date: [September 21, 2022, 3:36pm UTC](https://discourse.julialang.org/t/absolute-value-error/87579/3 "2022-09-21T15:36:10Z")
Perhaps some context is missing from your post. I have no problems (v 1.8.1, Intel Mac)
```julia
julia> v=rand(3); vnew=rand(3); subt=vnew-v;
julia> println(subt)
[2.32118e-01, -6.61210e-02, 2.67815e-01]
julia> di=abs.(subt);
julia> v = vnew;
julia> di
3-element Vector{Float64}:
2.32118e-01
6.61210e-02
2.67815e-01
```
---
### Author:  [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)
#### Post date: [September 21, 2022, 4:41pm UTC](https://discourse.julialang.org/t/absolute-value-error/87579/4 "2022-09-21T16:41:27Z")
You don’t happen to have a variable called `abs` or otherwise accidentally redefined the `abs` function?
What’s the full stacktrace?
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [September 21, 2022, 5:36pm UTC](https://discourse.julialang.org/t/absolute-value-error/87579/5 "2022-09-21T17:36:58Z")
> [@ejlongman](#):
>
> When I check the difference between two vectors then take the absolute value,
`abs.(subt)` is the _elementwise_ absolute value, which returns a vector. It sounds like you want the _norm_ of the difference, i.e. a single number `norm(vnew - v)`. (The [`norm` function](https://docs.julialang.org/en/v1/stdlib/LinearAlgebra/#LinearAlgebra.norm) is provided by the `LinearAlgebra` standard library.)
(Your `MethodError: no method matching isless` sounds like it is coming from a later line in your code, where you are comparing `di` to a scalar, e.g. you have `di ≤ sometolerance`, which fails because you can’t compare a vector to a scalar.)