# Use a variable column name to perform operation

**URL:** <https://discourse.julialang.org/t/use-a-variable-column-name-to-perform-operation/85458>\
**Category:** New to Julia\
**Created:** [August 8, 2022, 4:20am UTC](https://discourse.julialang.org/t/use-a-variable-column-name-to-perform-operation/85458 "2022-08-08T04:20:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![momo1](https://avatars.discourse-cdn.com/v4/letter/m/bbe5ce/32.png) [@momo1](https://discourse.julialang.org/u/momo1)\
**Post date:** [August 8, 2022, 4:20am UTC](https://discourse.julialang.org/t/use-a-variable-column-name-to-perform-operation/85458/1 "2022-08-08T04:20:17Z")

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Hi  
I’ve a code which needs to be robust to variable column name.  
I’ve tried the following which fails

```julia
var = mapwindow(cell -> mean(map(x -> columnnames(x)[findfirst(map(c -> startswith(string(c), "var_ "), columnnames(cell)))], cell)...), content, 1)

```

Previously, it was working with something like  
`# var = mapwindow(cell -> mean(map(x -> x.var_8, cell)...), content, 1)`  
so the column name in variable content can be anything like

> x.var\_8, x.var\_16, x.var\_3 etc

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<div class="post-metadata">

**Author:** ![nilshg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nilshg/32/2283_2.png) [@nilshg](https://discourse.julialang.org/u/nilshg)\
**Post date:** [August 8, 2022, 7:32am UTC](https://discourse.julialang.org/t/use-a-variable-column-name-to-perform-operation/85458/2 "2022-08-08T07:32:58Z")

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What is `x`? Where is `columnnames` defined?

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<div class="post-metadata">

**Author:** ![momo1](https://avatars.discourse-cdn.com/v4/letter/m/bbe5ce/32.png) [@momo1](https://discourse.julialang.org/u/momo1)\
**Post date:** [August 8, 2022, 11:58pm UTC](https://discourse.julialang.org/t/use-a-variable-column-name-to-perform-operation/85458/3 "2022-08-08T23:58:57Z")

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> [@momo1](#):
>
> `columnnames`

Its from Types Tables

> TypedTables.columnname