# Question about findmax
**URL:** https://discourse.julialang.org/t/question-about-findmax/45149
**Category:** General Usage
**Tags:** question
**Created:** [August 18, 2020, 9:33am UTC](https://discourse.julialang.org/t/question-about-findmax/45149 "2020-08-18T09:33:12Z")
**Posts on this page:** 15
**Page:** 1
### Author:  [@abcde](https://discourse.julialang.org/u/abcde)
#### Post date: [August 18, 2020, 9:33am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/1 "2020-08-18T09:33:12Z")
this is my code:
```julia
using StatsBase,DelimitedFiles
#function Characteristics(Data,)
global max_index_mean_var=Matrix{Matrix{Float64}}(undef,4*size(Data,1),size(Data,2))
# global mean_var=Matrix{Matrix{Float64}}(undef,2*size(Data,1),size(Data,2))
for i=1:size(Data,1)
j=1:size(Data,2)
#max_index_mean_var[4*i-3,j]=maximum(Data[i,j],dims=1)
max_index_mean_var[4*i-3,j]=getindex.(findmax(Data[i,j],dims=1)[1],1)
#max_index_mean_var[4*i-2,j]=getindex.(getindex(findmax(Data[i,j][1],dims=1),1))
#max_index_mean_var[4*i-1,j]=mean_and_var(Data[i,j],2)[1]
#max_index_mean_var[4*i,j]=mean_and_var(Data[i,j],2)[2]
end
```
this is the "Data"in my code :
this is the error:
ERROR: LoadError: MethodError: no method matching isless(::Array{Float64,2}, ::Array{Float64,2})
Closest candidates are:
isless(::Missing, ::Any) at missing.jl:87
isless(::Union{CategoricalString{R}, CategoricalValue{T,R} where T} where R, ::Any) at C:\Users\27990.juliapro\JuliaPro\_v1.4.2-1\packages\CategoricalArrays\dmrjI\src\value.jl:191
isless(::Any, ::Missing) at missing.jl:88
I tried to fix the code, but nothing worked,I don’t think this code is logically flawed,why???
please help me!thanks!!!
---
### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [August 18, 2020, 9:46am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/2 "2020-08-18T09:46:35Z")
This error here
> [@abcde](#):
>
> `ERROR: LoadError: MethodError: no method matching isless(::Array{Float64,2}, ::Array{Float64,2})`
indicates that `Data[i, j]` is _not_ a matrix, but an array of matrices. That means that `Data` is an array of arrays of arrays, instead of just an array of arrays. Can you try to figure that out? What are
```julia
typeof(Data)
```
and
```julia
typeof(Data[1,1])
```
?
You cannot call `findmax` on an array of arrays, since there is no defined method for determining if one array is greater than another (that’s the missing `isless` method.)
---
### Author:  [@abcde](https://discourse.julialang.org/u/abcde)
#### Post date: [August 18, 2020, 9:52am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/3 "2020-08-18T09:52:46Z")
```julia
global a=Matrix{Matrix{Float64}}(undef,5,2)
q=Matrix{Matrix{Float64}}(undef,5,2)
b=[1 22 13;11 5 6;7 8 9]
for i=1:10
j=1:2
global a[i]=b
end
for i=1:5
for j=1:2
q[i,j]=getindex.(findmax(a[i,j],dims=1)[1],1)
end
end
```
But this code works,why?
---
### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [August 18, 2020, 9:59am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/4 "2020-08-18T09:59:07Z")
> [@abcde](#):
>
> ```julia
> global a=Matrix{Matrix{Float64}}(undef,5,2)
> q=Matrix{Matrix{Float64}}(undef,5,2)
> b=[1 22 13;11 5 6;7 8 9]
> for i=1:10
> j=1:2
> global a[i]=b
> end
>
> for i=1:5
> for j=1:2
> q[i,j]=getindex.(findmax(a[i,j],dims=1)[1],1)
> end
> end
>
> ```
It works because `a[i, j]` is an ordinary matrix here, but that is not the case for `Data[i, j]`, apparently.
By the way, it is needlessly complicated to write
```julia
q[i,j]=getindex.(findmax(a[i,j],dims=1)[1],1)
```
Instead, just write
```julia
q[i, j] = maximum(a[i, j]; dims=1)
```
---
### Author:  [@abcde](https://discourse.julialang.org/u/abcde)
#### Post date: [August 18, 2020, 10:01am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/5 "2020-08-18T10:01:09Z")
They’re of the same type
---
### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [August 18, 2020, 10:03am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/6 "2020-08-18T10:03:20Z")
Can you run the following code:
```julia
typeof(Data)
```
And then
```julia
maximum(Data[1, 1]; dims=1)
```
?
(Sorry, I had a typo at first)
---
### Author:  [@abcde](https://discourse.julialang.org/u/abcde)
#### Post date: [August 18, 2020, 10:06am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/7 "2020-08-18T10:06:45Z")
---
### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [August 18, 2020, 10:10am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/8 "2020-08-18T10:10:31Z")
What happens if you run
```julia
global max_index_mean_var=Matrix{Matrix{Float64}}(undef,4*size(Data,1),size(Data,2))
# global mean_var=Matrix{Matrix{Float64}}(undef,2*size(Data,1),size(Data,2))
for i=1:size(Data,1)
j=1:size(Data,2)
#max_index_mean_var[4*i-3,j]=maximum(Data[i,j],dims=1)
max_index_mean_var[4*i-3,j]=getindex.(findmax(Data[i,j],dims=1)[1],1)
#max_index_mean_var[4*i-2,j]=getindex.(getindex(findmax(Data[i,j][1],dims=1),1))
#max_index_mean_var[4*i-1,j]=mean_and_var(Data[i,j],2)[1]
#max_index_mean_var[4*i,j]=mean_and_var(Data[i,j],2)[2]
end
```
now?
By the way, you should really avoid using globals, and make sure that your code are functions.
---
### Author:  [@abcde](https://discourse.julialang.org/u/abcde)
#### Post date: [August 18, 2020, 10:16am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/9 "2020-08-18T10:16:27Z")
it always does not work
---
### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [August 18, 2020, 10:50am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/10 "2020-08-18T10:50:50Z")
I’m afraid I cannot see what’s wrong here.
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [August 18, 2020, 11:16am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/11 "2020-08-18T11:16:16Z")
~~What is the output of:
```julia
q=Matrix{Any}(undef,size(Data,1),size(Data,2));
for i=1:size(Data,1)
for j=1:size(Data,2)
q[i,j]=typeof(Data[i,j])
end
end
unique(q)
```
~~~~ I hope it works, but the idea is clear? Output should be:
```julia
julia> unique(q)
1-element Array{Any,1}:
Array{Float64,2}
```
~~
---
### Author:  [@abcde](https://discourse.julialang.org/u/abcde)
#### Post date: [August 18, 2020, 11:28am UTC](https://discourse.julialang.org/t/question-about-findmax/45149/12 "2020-08-18T11:28:50Z")
thank you anyway!
---
### Author:  [@abcde](https://discourse.julialang.org/u/abcde)
#### Post date: [August 18, 2020, 2:44pm UTC](https://discourse.julialang.org/t/question-about-findmax/45149/14 "2020-08-18T14:44:21Z")
It’s supposed to be the error of the findmax function, but I’ve done other experiments, and everything else is correct except this one 😣
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [August 18, 2020, 3:00pm UTC](https://discourse.julialang.org/t/question-about-findmax/45149/15 "2020-08-18T15:00:47Z")
~~I suspect your Data structure has some wrong entries. Thats the test for to check if every single entry is of type ``` Array{Float64,2} ```~~
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [August 18, 2020, 7:36pm UTC](https://discourse.julialang.org/t/question-about-findmax/45149/16 "2020-08-18T19:36:59Z")
I see my error now 🙂